Variable magnification optical system and imaging apparatus

ABSTRACT

A variable magnification optical system consists of, in order from an object side to an image side, a first lens group, a second lens group, and a subsequent lens group. The variable magnification optical system satisfies a predetermined conditional expression for a partial dispersion ratio related to F line, C line, and a wavelength of 1970.09 nm, a d-line back focus of the variable magnification optical system at a telephoto end, a back focus in any one wavelength from a wavelength of 1300 nm to a wavelength of 2325.42 nm at the telephoto end, and a d-line focal length of the variable magnification optical system at the telephoto end.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. patent application Ser.No. 17/094,288, filed on Nov. 10, 2020, which claims priority under 35U.S.C. § 119 to Japanese Patent Application No. 2019-205022, filed onNov. 12, 2019. The above application is hereby expressly incorporated byreference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The technology of the present disclosure relates to a variablemagnification optical system and an imaging apparatus.

2. Description of the Related Art

In the related art, a variable magnification optical system has beenused for a distant monitoring camera at a national border, a forest, aharbor, and the like. In such an application, near-infrared light isused for imaging at night-time and imaging in a poor visibility statesuch as fog or smoke.

For example, a lens system disclosed in JP2016-095448A below is known asa variable magnification optical system in which near-infrared light isconsidered. In JP2016-095448A, a zoom lens composed of, in order from anobject side to an image side, a first lens group having a positiverefractive power, a second lens group having a negative refractivepower, a third lens group having a negative refractive power, and afourth lens group having a positive refractive power is disclosed.

SUMMARY OF THE INVENTION

In the near-infrared light, short wave infra-red (SWIR) light that maybe classified as a spectrum of a wavelength of 1000 nm to 2500 nm hashigh usability. In recent years, there has been an increasing demand fora lens system in which chromatic aberration is corrected across awavelength range of a visible range to an SWIR range. In a case wherefavorable maintenance of other optical characteristics whileimplementing correction of the chromatic aberration in such a widespectrum is desired, a size of the lens system is likely to beincreased. However, in recent years, there is also a high demand forcompactness of an apparatus.

The present disclosure is conceived in view of the above matter, and anobject thereof is to provide a variable magnification optical systemthat has favorable characteristics and in which chromatic aberration iscorrected in a wavelength range of a visible range to an SWIR rangewhile an increase in size of a lens system is suppressed, and an imagingapparatus comprising the variable magnification optical system.

A variable magnification optical system according to a first aspect ofthe present disclosure consists of, in order from an object side to animage side, a first lens group, a second lens group, and a subsequentlens group, in which all intervals between adjacent lens groups arechanged during zooming, and in a case where a d-line back focus in anair-conversion distance of an entire system at a telephoto end isdenoted by Bfd, a back focus in any one wavelength from a wavelength of1300 nm to a wavelength of 2325.42 nm in the air-conversion distance ofthe entire system at the telephoto end is denoted by BfIR, a d-linefocal length of the entire system at the telephoto end is denoted by ft,a refractive index in F line is denoted by nF, a refractive index in Cline is denoted by nC, a refractive index in a wavelength of 1970.09 nmis denoted by n1970, and a partial dispersion ratio θ is defined asθ=(nC−n1970)/(nF−nC) for each lens of all lens groups, and an average ofθ of all lenses of the first lens group is denoted by θ1ave, ConditionalExpressions (1) and (2) are satisfied.

−0.0022<(Bfd−BfIR)/ft  (1)

1.3<θ1 ave  (2)

A variable magnification optical system according to a second aspect ofthe present disclosure consists of, in order from an object side to animage side, a first lens group, a second lens group, and a subsequentlens group, in which all intervals between adjacent lens groups arechanged during zooming, and in a case where a d-line back focus in anair-conversion distance of an entire system at a telephoto end isdenoted by Bfd, a back focus in any one wavelength from a wavelength of1300 nm to a wavelength of 2325.42 nm in the air-conversion distance ofthe entire system at the telephoto end is denoted by BfIR, a d-linefocal length of the entire system at the telephoto end is denoted by ft,a refractive index in F line is denoted by nF, a refractive index in Cline is denoted by nC, a refractive index in a wavelength of 1970.09 nmis denoted by n1970, and a partial dispersion ratio θ is defined asθ=(nC−n1970)/(nF−nC) for each lens of all lens groups, an average of θof all positive lenses of the first lens group is denoted by θ1P ave,and an average of θ of all negative lenses of the first lens group isdenoted by θ1Nave, Conditional Expressions (1) and (3) are satisfied.

−0.0022<(Bfd−BfIR)/ft  (1)

−0.8<θ1P ave−θ1N ave<0.8  (3)

In a variable magnification optical system according to a third aspectof the present disclosure, the variable magnification optical systemcomprises the first lens group, the second lens group, a third lensgroup, and a fourth lens group consecutively in order from the objectside to the image side, as the lens groups, all intervals betweenadjacent lens groups are changed during zooming, and in a case where ad-line back focus in an air-conversion distance of an entire system at atelephoto end is denoted by Bfd, a back focus in any one wavelength froma wavelength of 1300 nm to a wavelength of 2325.42 nm in theair-conversion distance of the entire system at the telephoto end isdenoted by BfIR, a d-line focal length of the entire system at thetelephoto end is denoted by ft, a refractive index in F line is denotedby nF, a refractive index in C line is denoted by nC, a refractive indexin a wavelength of 1970.09 nm is denoted by n1970, and a partialdispersion ratio θ is defined as θ=(nC−n1970)/(nF−nC) for each lens ofall lens groups, and an average of θ of all lenses of the third lensgroup is denoted by θ3ave, Conditional Expressions (1) and (4) aresatisfied.

−0.0022<(Bfd−BfIR)/ft  (1)

1.4<θ3 ave  (4)

It is preferable that the variable magnification optical systemaccording to the first, second, and third aspects satisfies at least oneof Conditional Expression (5), (6), or (10) to (13) below.

0.3<ft/TL  (5)

0.3<θ1 ave/θ2 ave<2  (6)

1.2<θ2 ave  (10)

1.6<θ1P ave<2.3  (11)

θ1N ave<2.3  (12)

−2<θ2P ave−θ2N ave  (13)

where

ft: d-line focal length of entire system at telephoto end

TL: sum of distance on optical axis from lens surface of variablemagnification optical system closest to object side to lens surface ofvariable magnification optical system closest to image side at telephotoend, and d-line back focus in air-conversion distance of entire systemat telephoto end

θ1 ave: average of θ of all lenses of first lens group

θ1P ave: average of θ of all positive lenses of first lens group

θ1N ave: average of θ of all negative lenses of first lens group

θ2 ave: average of θ of all lenses of second lens group

θ2P ave: average of θ of all positive lenses of second lens group

θ2N ave: average of θ of all negative lenses of second lens group

It is preferable that in the variable magnification optical systemaccording to the first, second, and third aspects, the variablemagnification optical system comprises the first lens group, the secondlens group, a third lens group, and a fourth lens group consecutively inorder from the object side to the image side, as the lens groups, andsatisfies at least one of Conditional Expression (7), (9), (14), or (15)below.

0.3<θ3 ave/θ2 ave<2  (7)

1.3<θ4 ave  (9)

θ3P ave−θ3N ave<2  (14)

−2<04P ave−θ4N ave<2  (15)

where

θ2 ave: average of θ of all lenses of second lens group

θ3 ave: average of θ of all lenses of third lens group

θ4 ave: average of θ of all lenses of fourth lens group

θ3P ave: average of θ of all positive lenses of third lens group

θ3N ave: average of θ of all negative lenses of third lens group

θ4P ave: average of θ of all positive lenses of fourth lens group

θ4N ave: average of θ of all negative lenses of fourth lens group

It is preferable that in a case where a refractive index in d line isdenoted by nd, a refractive index in F line is denoted by nF, arefractive index in C line is denoted by nC, and an Abbe number v isdefined as v=(nd−1)/(nF−nC) for each lens of all lens groups, thevariable magnification optical system according to the first, second,and third aspects satisfies at least one of Conditional Expression (8)or (16) below.

50<v1ave  (8)

15<v1P ave−v1N ave  (16)

where

v1 ave: average of v of all lenses of first lens group

v1P ave: average of v of all positive lenses of first lens group

v1N ave: average of v of all negative lenses of first lens group

It is preferable that in the variable magnification optical systemaccording to the first, second, and third aspects, the variablemagnification optical system comprises only four lens groups consistingof the first lens group, the second lens group, a third lens group, anda fourth lens group in order from the object side to the image side, asthe lens groups, and the first lens group has a positive refractivepower, the second lens group has a negative refractive power, the thirdlens group has a positive refractive power, and the fourth lens grouphas a positive or negative refractive power.

An imaging apparatus according to another aspect of the presentdisclosure comprises the variable magnification optical system accordingto the aspect of the present disclosure.

In the present specification, “consists of . . . ” and “consisting of .. . ” intend to include a lens substantially not having a refractivepower, an optical element other than a lens like a stop, a filter, andcover glass, a mechanism part such as a lens flange, a lens barrel, animaging element, and a camera shake correction mechanism besides exampleconstituents.

In the present specification, a “lens group” refers to a set of lensesthat are moved or fixed in units of lens groups during zooming and inwhich an interval between lenses in the group is not changed. A “ . . .group having a positive refractive power” means that the group as awhole has a positive refractive power. Similarly, a “ . . . group havinga negative refractive power” means that the group as a whole has anegative refractive power. A “lens having a positive refractive power”and a “positive lens” have the same meaning. A “lens having a negativerefractive power” and a “negative lens” have the same meaning. A “ . . .lens group” is not limited to a configuration consisting of a pluralityof lenses and may have a configuration consisting of only one lens.

A compound aspherical lens (lens in which a spherical lens and a film ofan aspherical shape formed on the spherical lens are configured to beintegrated and that, as a whole, functions as one aspherical lens) isnot regarded as a cemented lens and is treated as one lens. A sign of arefractive power and a surface shape related to a lens having anaspherical surface are considered in a paraxial region.

In the present specification, the “entire system” means the “variablemagnification optical system”. The “back focus” is a distance on theoptical axis from a lens surface closest to the image side to a focalposition on the image side. The “focal length” used in the conditionalexpressions is a paraxial focal length. Values used in the conditionalexpressions are values in a state where an object at infinity isfocused. In the present specification, “d line”, “C line”, “F line”, “gline”, and “t line” are bright lines. A wavelength of d line is 587.56nm. A wavelength of C line is 656.27 nm. A wavelength of F line is486.13 nm. A wavelength of g line is 435.83 nm. A wavelength oft line is1013.98 nm. In the present specification, “near-infrared” means aspectrum of a wavelength of 700 nm to 2500 nm, and “SWIR” means aspectrum of a wavelength of 1000 nm to 2500 nm. In addition, “nm” usedas a unit of wavelength is nanometer.

According to the technology of the present disclosure, a variablemagnification optical system that has favorable characteristics and inwhich chromatic aberration is corrected in a wavelength range of avisible range to an SWIR range while an increase in size of a lenssystem is suppressed, and an imaging apparatus comprising the variablemagnification optical system can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a configuration of a variablemagnification optical system according to one embodiment of the presentdisclosure and a diagram illustrating a movement trajectory, thevariable magnification optical system corresponding to a variablemagnification optical system of Example 1 of the present disclosure.

FIG. 2 is a cross-sectional view illustrating the configuration andluminous flux of the variable magnification optical system illustratedin FIG. 1 .

FIG. 3 is each aberration diagram of the variable magnification opticalsystem of Example 1 of the present disclosure.

FIG. 4 is a cross-sectional view of a configuration of a variablemagnification optical system of Example 2 of the present disclosure anda diagram illustrating a movement trajectory.

FIG. 5 is each aberration diagram of the variable magnification opticalsystem of Example 2 of the present disclosure.

FIG. 6 is a cross-sectional view of a configuration of a variablemagnification optical system of Example 3 of the present disclosure anda diagram illustrating a movement trajectory.

FIG. 7 is each aberration diagram of the variable magnification opticalsystem of Example 3 of the present disclosure.

FIG. 8 is a cross-sectional view of a configuration of a variablemagnification optical system of Example 4 of the present disclosure anda diagram illustrating a movement trajectory.

FIG. 9 is each aberration diagram of the variable magnification opticalsystem of Example 4 of the present disclosure.

FIG. 10 is a cross-sectional view of a configuration of a variablemagnification optical system of Example 5 of the present disclosure anda diagram illustrating a movement trajectory.

FIG. 11 is each aberration diagram of the variable magnification opticalsystem of Example 5 of the present disclosure.

FIG. 12 is a cross-sectional view of a configuration of a variablemagnification optical system of Example 6 of the present disclosure anda diagram illustrating a movement trajectory.

FIG. 13 is each aberration diagram of the variable magnification opticalsystem of Example 6 of the present disclosure.

FIG. 14 is a cross-sectional view of a configuration of a variablemagnification optical system of Example 7 of the present disclosure anda diagram illustrating a movement trajectory.

FIG. 15 is each aberration diagram of the variable magnification opticalsystem of Example 7 of the present disclosure.

FIG. 16 is a cross-sectional view of a configuration of a variablemagnification optical system of Example 8 of the present disclosure anda diagram illustrating a movement trajectory.

FIG. 17 is each aberration diagram of the variable magnification opticalsystem of Example 8 of the present disclosure.

FIG. 18 is a cross-sectional view of a configuration of a variablemagnification optical system of Example 9 of the present disclosure anda diagram illustrating a movement trajectory.

FIG. 19 is each aberration diagram of the variable magnification opticalsystem of Example 9 of the present disclosure.

FIG. 20 is a cross-sectional view of a configuration of a variablemagnification optical system of Example 10 of the present disclosure anda diagram illustrating a movement trajectory.

FIG. 21 is each aberration diagram of the variable magnification opticalsystem of Example 10 of the present disclosure.

FIG. 22 is a cross-sectional view of a configuration of a variablemagnification optical system of Example 11 of the present disclosure anda diagram illustrating a movement trajectory.

FIG. 23 is each aberration diagram of the variable magnification opticalsystem of Example 11 of the present disclosure.

FIG. 24 is a schematic configuration diagram of an imaging apparatusaccording to one embodiment of the present disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment according to the technology of the presentdisclosure will be described with reference to the drawings. FIG. 1 is across-sectional view illustrating a configuration at a wide angle end ofa variable magnification optical system according to one embodiment ofthe present disclosure and a diagram illustrating a movement trajectory.FIG. 2 is a cross-sectional view illustrating the configuration andluminous flux of the variable magnification optical system. Examplesillustrated in FIG. 1 and FIG. 2 correspond to a variable magnificationoptical system of Example 1 described later. In the cross-sectional viewof FIG. 1 and FIG. 2 , a state where an object at infinity is focused isillustrated. A left side is an object side, and a right side is an imageside. In FIG. 2 , a wide angle end state is illustrated in an upper partdenoted by “WIDE”. A middle focal length state is illustrated in amiddle part denoted by “MIDDLE”. A telephoto end state is illustrated ina lower part denoted by “TELE”. In FIG. 2 , axial luminous flux wa andluminous flux wb of the maximum angle of view in the wide angle endstate, axial luminous flux ma and luminous flux mb of the maximum angleof view in the middle focal length state, and axial luminous flux to andluminous flux tb of the maximum angle of view in the telephoto end stateare illustrated as the luminous flux. Hereinafter, description will bemainly provided with reference to FIG. 1 .

In FIG. 1 , an example in which an optical member PP having a parallelflat plate shape is arranged between the variable magnification opticalsystem and an image plane Sim is illustrated by considering applicationof the variable magnification optical system to an imaging apparatus.The optical member PP is a member considered to include various filtersand/or cover glass and the like. For example, various filters include alow-pass filter, an infrared cut-off filter, and a filter that cuts offa specific wavelength range. The optical member PP is a member nothaving a refractive power. It can also be configured that the opticalmember PP is omitted.

The variable magnification optical system of the example illustrated inFIG. 1 consists of, in order from the object side to the image side, afirst lens group G1, a second lens group G2, and a subsequent lens groupGR. The subsequent lens group GR of the example illustrated in FIG. 1consists of, in order from the object side to the image side, a thirdlens group G3, an aperture stop St, and a fourth lens group G4. That is,the variable magnification optical system comprises, consecutively inorder from the object side to the image side, the first lens group G1,the second lens group G2, the third lens group G3, and the fourth lensgroup G4 as lens groups. Using the variable magnification optical systemhaving a four-group configuration is advantageous for favorablecorrection of chromatic aberration and maintenance of favorablecharacteristics in a wavelength range of a visible range to an SWIRrange even during zooming.

The aperture stop St in FIG. 1 does not indicate a shape and indicates aposition on an optical axis.

For example, each lens group can be configured such that the first lensgroup G1 has a positive refractive power, the second lens group G2 has anegative refractive power, the third lens group G3 has a positiverefractive power, and the fourth lens group G4 has a positive ornegative refractive power. Using the first lens group G1 having apositive refractive power is advantageous for decreasing a total lengthof a lens system. Using the second lens group G2 having a negativerefractive power is advantageous for obtaining a high magnification.Using the third lens group G3 having a positive refractive power isadvantageous for decreasing the total length of the lens system. In acase where the fourth lens group G4 has a positive refractive power, anadvantage for decreasing the total length of the lens system isachieved. In a case where the fourth lens group G4 has a negativerefractive power, an advantage for securing a long back focus isachieved.

In the example in FIG. 1 , during zooming, the first lens group G1 andthe fourth lens group G4 are fixed with respect to the image plane Sim,and the second lens group G2 and the third lens group G3 are moved alongan optical axis Z by changing an interval between each other. In FIG. 1, a movement trajectory of each lens group during zooming from a wideangle end to a telephoto end is schematically illustrated by a solidline arrow below each of the second lens group G2 and the third lensgroup G3. A configuration in which a distance from a lens surfaceclosest to the object side to a lens surface closest to the image sideis not changed during zooming as in the example illustrated in FIG. 1 isadvantageous in terms of dust-proofness.

For example, in the variable magnification optical system in FIG. 1 ,the first lens group G1 consists of, in order from the object side tothe image side, five lenses including lenses L11 to L15. The second lensgroup G2 consists of, in order from the object side to the image side,five lenses including lenses L21 to L25. The third lens group G3consists of, in order from the object side to the image side, fourlenses including lenses L31 to L34. The fourth lens group G4 consistsof, in order from the object side to the image side, 17 lenses includinglenses L41 to L57. Each lens group of the example in FIG. 1 isconfigured to include at least one positive lens and at least onenegative lens.

The variable magnification optical system according to the embodiment ofthe technology of the present disclosure is configured to satisfyConditional Expression (1) below.

−0.0022<(Bfd−BfIR)/ft  (1)

where

Bfd: d-line back focus in air-conversion distance of entire system attelephoto end

BfIR: back focus in air-conversion distance of entire system attelephoto end in any one wavelength from wavelength of 1300 nm towavelength of 2325.42 nm

ft: d-line focal length of entire system at telephoto end

-   -   The variable magnification optical system according to the        embodiment of the technology of the present disclosure may        satisfy Conditional Expression (1) for BfIR related to at least        one wavelength from a wavelength of 1300 nm to a wavelength of        2325.42 nm.

Materials of lenses of the variable magnification optical systemaccording to the embodiment of the technology of the present disclosureare selected by considering the wavelength range including the visiblerange and the SWIR range. In the technology of the present disclosure,an Abbe number and a partial dispersion ratio are defined as follows.That is, for each lens of all lens groups, a d-line refractive index isdenoted by nd. An F-line refractive index is denoted by nF. A C-linerefractive index is denoted by nC. A refractive index in a wavelength of1970.09 nm is denoted by n1970. An abbe number v and a partialdispersion ratio θ are defined as v=(nd−1)/(nF−nC) andθ=(nC−n1970)/(nF−nC), respectively. Here, v is an Abbe number based on dline. In addition, θ is a partial dispersion ratio between C line and awavelength of 1970.09 nm.

It is preferable that the variable magnification optical systemaccording to the embodiment of the technology of the present disclosuresatisfies at least one of Conditional Expressions (2) to (31) belowincluding conditional expressions related to v or θ defined above.

1.3<θ1 ave  (2)

−0.8<θ1P ave−θ1N ave<0.8  (3)

1.4<θ3 ave  (4)

0.3<ft/TL  (5)

0.3<θ1 ave/θ2 ave<2  (6)

0.3<θ3 ave/θ2 ave<2  (7)

50<v1 ave  (8)

1.3<θ4 ave  (9)

1.2<θ2 ave  (10)

1.6<θ1P ave<2.3  (11)

θ1N ave<2.3  (12)

−2<θ2P ave−θ2N ave  (13)

θ3P ave−θ3Nave<2  (14)

−2<04P ave−θ4Nave<2  (15)

15<v1P ave−v1N ave  (16)

v2P ave−v2N ave<−5  (17)

15<v3P ave−v3N ave  (18)

20<v2 ave<65  (19)

30<v3 ave  (20)

30<v4 ave  (21)

θ2P ave<2.2  (22)

1.35<θ2N ave  (23)

θ4P ave<2.2  (24)

0.3<ft/f1  (25)

1<ft/f1P max  (26)

−10<f2/fw<−0.1  (27)

−10<f2N max/fw  (28)

f1/f2<−0.5  (29)

−10<f3/f2<−0.1  (30)

0.3<TL/f31  (31)

where

θ1 ave: average of θ of all lenses of first lens group

θ1P ave: average of θ of all positive lenses of first lens group

θ1N ave: average of θ of all negative lenses of first lens group

θ2 ave: average of θ of all lenses of second lens group

θ3 ave: average of θ of all lenses of third lens group

θ4 ave: average of θ of all lenses of fourth lens group

θ2P ave: average of θ of all positive lenses of second lens group

θ2N ave: average of θ of all negative lenses of second lens group

θ3P ave: average of θ of all positive lenses of third lens group

θ3N ave: average of θ of all negative lenses of third lens group

θ4P ave: average of θ of all positive lenses of fourth lens group

θ4N ave: average of θ of all negative lenses of fourth lens group

v1 ave: average of v of all lenses of first lens group

v2 ave: average of v of all lenses of second lens group

v3 ave: average of v of all lenses of third lens group

v4 ave: average of v of all lenses of fourth lens group

v1P ave: average of v of all positive lenses of first lens group

v1N ave: average of v of all negative lenses of first lens group

v2P ave: average of v of all positive lenses of second lens group

v2N ave: average of v of all negative lenses of second lens group

v3P ave: average of v of all positive lenses of third lens group

v3N ave: average of v of all negative lenses of third lens group

fw: d-line focal length of entire system at wide angle end

ft: d-line focal length of entire system at telephoto end

TL: sum of distance on optical axis from lens surface of variablemagnification optical system closest to object side to lens surface ofvariable magnification optical system closest to image side at telephotoend, and d-line back focus in air-conversion distance of entire systemat telephoto end

f1 : focal length of first lens group

f2: focal length of second lens group

f3: focal length of third lens group

f31: focal length of lens of third lens group closest to object side

f1P max: focal length of positive lens having highest refractive poweramong all positive lenses of first lens group

f2N max: focal length of negative lens having highest refractive poweramong all negative lenses of second lens group

Hereinafter, the above conditional expressions will be described. Bysatisfying Conditional Expression (1), it is easy to correct axialchromatic aberration from the visible range to the SWIR range.

Here, (Bfd−BfIR)/ft is preferably greater than −0.002, more preferablygreater than −0.00125, further preferably greater than −0.001, andfurther more preferably greater than −0.0008.

It is preferable that (Bfd−BfIR)/ft is less than 0.005. In this case, itis easy to correct the axial chromatic aberration from the visible rangeto the SWIR range. Here, (Bfd−BfIR)/ft is more preferably less than0.0022, further preferably less than 0.002, further more preferably lessthan 0.00125, still more preferably less than 0.001, and yet still morepreferably less than 0.0008.

By satisfying Conditional Expression (2), it is easy to correct theaxial chromatic aberration from the visible range to the SWIR range.Here, θ1ave is more preferably greater than 1.5, further preferablygreater than 1.6, further more preferably greater than 1.7, still morepreferably greater than 1.8, and yet still more preferably greater than1.9.

In addition, θ1ave is preferably less than 2.4. In this case, it is easyto use a large number of lenses having a high refractive index in thefirst lens group G1, and it is easy to reduce a size of the first lensgroup G1. Here, θ1ave is more preferably less than 2.35, furtherpreferably less than 2.3, further more preferably less than 2.2, andstill more preferably less than 2.15.

By satisfying Conditional Expression (3), it is easy to decrease anabsolute value of a difference between a partial dispersion ratio of apositive lens and a partial dispersion ratio of a negative lens, and itis easy to correct a second-order spectrum of the axial chromaticaberration from the visible range to the SWIR range. Here, θ1P ave−θ1Nave is more preferably greater than −0.5, further preferably greaterthan −0.4, further more preferably greater than −0.3, still morepreferably greater than −0.2, yet still more preferably greater than−0.1, and further still more preferably greater than 0.

In addition, θ1P ave−θ1N ave is more preferably less than 0.5, furtherpreferably less than 0.4, further more preferably less than 0.3, andstill more preferably less than 0.2.

By satisfying Conditional Expression (4), it is easy to correct theaxial chromatic aberration from the visible range to the SWIR range.Here, θ3ave is more preferably greater than 1.5, further preferablygreater than 1.6, and further more preferably greater than 1.7.

In addition, θ3ave is preferably less than 2.3. In this case, it is easyto use a large number of lenses having a high refractive index in thethird lens group G3, and it is easy to reduce a size of the third lensgroup G3. Here, θ3ave is more preferably less than 2.2, furtherpreferably less than 2.1, and further more preferably less than 2.

In Conditional Expression (5), TL is the d-line total length of the lenssystem. By satisfying Conditional Expression (5), it is easy to suppressan increase in total length of the lens system. Here, ft/TL is morepreferably greater than 0.5, further preferably greater than 1, furthermore preferably greater than 1.1, still more preferably greater than1.5, yet still more preferably greater than 1.6, and further still morepreferably greater than 1.7.

In addition, ft/TL is preferably less than 30. In this case, the totallength of the lens system is not excessively decreased. Thus, it is easyto increase a magnification. Here, ft/TL is more preferably less than20, further preferably less than 10, further more preferably less than8, and still more preferably less than 5.

By satisfying Conditional Expression (6), balance between second-orderspectrums of the first lens group G1 and the second lens group G2 can beappropriately maintained, and it is easy to correct the axial chromaticaberration at the telephoto end. Here, θ1ave/θ2 ave is more preferablygreater than 0.5, further preferably greater than 0.7, further morepreferably greater than 0.8, and still more preferably greater than 0.9.

In addition, θ1ave/θ2 ave is more preferably less than 1.8, furtherpreferably less than 1.7, and further more preferably less than 1.6.

By satisfying Conditional Expression (7), balance between second-orderspectrums of the second lens group G2 and the third lens group G3 can beappropriately maintained, and it is easy to correct the axial chromaticaberration at the telephoto end. Here, θ3ave/θ2 ave is more preferablygreater than 0.5, further preferably greater than 0.7, further morepreferably greater than 0.8, and still more preferably greater than 0.9.

In addition, θ3ave/θ2 ave is more preferably less than 1.8, furtherpreferably less than 1.7, further more preferably less than 1.6, andstill more preferably less than 1.5.

By satisfying Conditional Expression (8), an Abbe number of a positivelens and an Abbe number of a negative lens constituting the first lensgroup G1 can be appropriately distributed. Thus, it is easy to correctthe axial chromatic aberration. More specifically, by satisfyingConditional Expression (8), a decrease in Abbe number of a lens of thefirst lens group G1 can be prevented. Thus, in the first lens group G1,it is easy to secure a difference between the Abbe number of thepositive lens and the Abbe number of the negative lens while decreasingan absolute value of a difference between a partial dispersion ratio ofthe positive lens and a partial dispersion ratio of the negative lens.Accordingly, it is easy to correct the second-order spectrum of theaxial chromatic aberration. Here, v1ave is more preferably greater than55, further preferably greater than 60, further more preferably greaterthan 65, and still more preferably greater than 69.

In addition, in order to appropriately distribute the Abbe numbers,v1ave is preferably less than 95. In this case, an excessive increase inAbbe number of the lens of the first lens group G1 can be suppressed.Thus, in the first lens group G1, it is easy to increase the absolutevalue of the difference between the Abbe number of the positive lens andthe Abbe number of the negative lens, and it is easy to correct theaxial chromatic aberration. Here, v1ave is more preferably less than 90,and further preferably less than 85.

By satisfying Conditional Expression (9), it is easy to correct theaxial chromatic aberration from the visible range to the SWIR range.Here, θ4 ave is more preferably greater than 1.4, further preferablygreater than 1.5, further more preferably greater than 1.6, and stillmore preferably greater than 1.7.

In addition, θ4 ave is preferably less than 2.3. In this case, it iseasy to use a large number of lenses having a high refractive index inthe fourth lens group G4, and it is easy to reduce a size of the fourthlens group G4. Here, θ4 ave is more preferably less than 2.2, furtherpreferably less than 2.1, further more preferably less than 2, and stillmore preferably less than 1.95.

By satisfying Conditional Expression (10), it is easy to correct theaxial chromatic aberration from the visible range to the SWIR range.Here, θ2 ave is more preferably greater than 1.4, further preferablygreater than 1.5, and further more preferably greater than 1.6.

In addition, θ2 ave is preferably less than 2.3. In this case, it iseasy to use a large number of lenses having a high refractive index inthe second lens group G2, and it is easy to reduce a size of the secondlens group G2. Here, θ2 ave is more preferably less than 2.2, furtherpreferably less than 2.1, further more preferably less than 2, and stillmore preferably less than 1.95.

By satisfying Conditional Expression (11) not to be below a lower limitthereof, it is easy to correct the axial chromatic aberration. Here, θ1Pave is more preferably greater than 1.7, further preferably greater than1.8, and further more preferably greater than 1.9.

In addition, by satisfying Conditional Expression (11) not to be abovean upper limit thereof, it is easy to use a large number of lenseshaving a high refractive index as the positive lens of the first lensgroup G1, and it is easy to reduce the size of the first lens group G1.Here, θ1P ave is more preferably less than 2.25, further preferably lessthan 2.2, and further more preferably less than 2.15.

By satisfying Conditional Expression (12), it is easy to decrease theabsolute value of the difference between the partial dispersion ratio ofthe positive lens and the partial dispersion ratio of the negative lensin the first lens group G1, and it is easy to correct the second-orderspectrum of the axial chromatic aberration. Here, θ1N ave is morepreferably less than 2.25, and further more preferably less than 2.2.

In addition, θ1N ave is preferably greater than 1.5. In this case, it iseasy to secure the difference between the Abbe number of the positivelens and the Abbe number of the negative lens while decreasing theabsolute value of the difference between the partial dispersion ratio ofthe positive lens and the partial dispersion ratio of the negative lensin the first lens group G1, and it is easy to correct the axialchromatic aberration. Here, θ1N ave is more preferably greater than 1.6,further preferably greater than 1.7, and further more preferably greaterthan 1.8.

By satisfying Conditional Expression (13), it is easy to suppress anincrease in absolute value of a difference between a partial dispersionratio of a positive lens and a partial dispersion ratio of a negativelens in the second lens group G2, and it is easy to correct thesecond-order spectrum of the axial chromatic aberration. Here, θ2Pave−θ2N ave is more preferably greater than −1.5, further preferablygreater than −1, further more preferably greater than −0.8, and stillmore preferably greater than −0.7.

In addition, θ2P ave−θ2N ave is preferably less than 0. In this case,the partial dispersion ratio of the positive lens in the second lensgroup G2 can be set to be less than the partial dispersion ratio of thenegative lens, and it is easy to correct the second-order spectrum ofthe axial chromatic aberration by combining the first lens group G1 withthe second lens group G2. Here, θ2P ave−θ2N ave is more preferably lessthan −0.01, further more preferably less than - 0.03, and still morepreferably less than −0.05.

By satisfying Conditional Expression (14), it is easy to decrease anabsolute value of a difference between a partial dispersion ratio of apositive lens and a partial dispersion ratio of a negative lens in thethird lens group G3, and it is easy to correct the second-order spectrumof the axial chromatic aberration. Here, θ3P ave−θ3N ave is morepreferably less than 1.5, further preferably less than 1, further morepreferably less than 0.8, and still more preferably less than 0.7.

In addition, θ3P ave−θ3N ave is preferably greater than 0. In this case,the partial dispersion ratio of the positive lens in the third lensgroup G3 can be set to be greater than the partial dispersion ratio ofthe negative lens, and it is easy to correct the second-order spectrumof the axial chromatic aberration by combining the third lens group G3with other lens groups. Here, θ3P ave−θ3N ave is more preferably greaterthan 0.01, further preferably greater than 0.05, and further morepreferably greater than 0.1.

By satisfying Conditional Expression (15), it is easy to decrease anabsolute value of a difference between a partial dispersion ratio of apositive lens and a partial dispersion ratio of a negative lens in thefourth lens group G4, and it is easy to correct the second-orderspectrum of the axial chromatic aberration. Here, θ4P ave−θ4N ave ismore preferably greater than −1, further preferably greater than −0.8,and further more preferably greater than −0.6.

In addition, θ4P ave−θ4N ave is more preferably less than 1, furtherpreferably less than 0.5, and further more preferably less than 0.3.

By satisfying Conditional Expression (16), it is easy to secure thedifference between the Abbe number of the positive lens and the Abbenumber of the negative lens in the first lens group G1, and it is easyto correct the axial chromatic aberration from the visible range to theSWIR range. Here, v1P ave−v1N ave is more preferably greater than 18,further preferably greater than 20, and further more preferably greaterthan 25.

In addition, v1P ave−v1N ave is preferably less than 50. In this case,the absolute value of the difference between the partial dispersionratio of the positive lens and the partial dispersion ratio of thenegative lens can be decreased, and it is easy to suppress thesecond-order spectrum of the axial chromatic aberration from the visiblerange to the SWIR range. Generally, in a case where the absolute valueof the difference between the Abbe number of the positive lens and theAbbe number of the negative lens is increased, the partial dispersionratio of the positive lens tends to be increased, and the partialdispersion ratio of the negative lens tends to be decreased. Then, it isdifficult to perform achromatization by combining a positive lens and anegative lens having similar partial dispersion ratios, and thesecond-order spectrum is increased. Here, v1P ave−v1N ave is morepreferably less than 40, and further preferably less than 38.

By satisfying Conditional Expression (17), it is easy to secure adifference between an Abbe number of a positive lens and an Abbe numberof a negative lens in the second lens group G2, and it is easy tocorrect the axial chromatic aberration from the visible range to theSWIR range. Here, v2P ave−v2N ave is more preferably less than −8,further preferably less than −10, and further more preferably less than−13.

In addition, v2P ave−v2N ave is preferably greater than −50. In thiscase, it is easy to decrease the absolute value of the differencebetween the partial dispersion ratio of the positive lens and thepartial dispersion ratio of the negative lens, and it is easy to correctthe second- order spectrum of the axial chromatic aberration. Here, v2Pave−v2N ave is more preferably greater than −40, and further preferablygreater than −30.

By satisfying Conditional Expression (18), it is easy to secure adifference between an Abbe number of a positive lens and an Abbe numberof a negative lens in the third lens group G3, and it is easy to correctthe axial chromatic aberration from the visible range to the SWIR range.Here, v3P ave−v3N ave is more preferably greater than 20, and furtherpreferably greater than 25.

In addition, v3P ave−v3N ave is preferably less than 65. In this case,as in a case of an upper limit of Conditional Expression (16), theabsolute value of the difference between the partial dispersion ratio ofthe positive lens and the partial dispersion ratio of the negative lenscan be decreased, and it is easy to suppress the second-order spectrumof the axial chromatic aberration from the visible range to the SWIRrange. Here, v3P ave−v3N ave is more preferably less than 60, andfurther preferably less than 50.

By satisfying Conditional Expression (19), the Abbe number of thepositive lens and the Abbe number of the negative lens constituting thesecond lens group G2 can be appropriately distributed. Thus, it is easyto correct the axial chromatic aberration. More specifically, bysatisfying Conditional Expression (19) not to be below a lower limitthereof, a decrease in Abbe number of a lens of the second lens group G2can be prevented. Thus, in the second lens group G2, it is easy tosecure a difference between the Abbe number of the positive lens and theAbbe number of the negative lens while decreasing the absolute value ofthe difference between the partial dispersion ratio of the positive lensand the partial dispersion ratio of the negative lens. Accordingly, itis easy to correct the second-order spectrum of the axial chromaticaberration. Here, v2ave is more preferably greater than 25, furtherpreferably greater than 28, and further more preferably greater than 35.

By satisfying Conditional Expression (19) not to be above an upper limitthereof, an excessive increase in Abbe number of the lens of the secondlens group G2 can be suppressed. Thus, in the second lens group G2, itis easy to increase an absolute value of the difference between the Abbenumber of the positive lens and the Abbe number of the negative lens inthe second lens group G2, and it is easy to correct the axial chromaticaberration. Here, v2ave is more preferably less than 60, and furtherpreferably less than 57.

By satisfying Conditional Expression (20), the Abbe number of thepositive lens and the Abbe number of the negative lens constituting thethird lens group G3 can be appropriately distributed. Thus, it is easyto correct the axial chromatic aberration. More specifically, bysatisfying Conditional Expression (20), a decrease in Abbe number of alens of the third lens group G3 can be prevented. Thus, in the thirdlens group G3, it is easy to secure a difference between the Abbe numberof the positive lens and the Abbe number of the negative lens whiledecreasing the absolute value of the difference between the partialdispersion ratio of the positive lens and the partial dispersion ratioof the negative lens. Accordingly, it is easy to correct thesecond-order spectrum of the axial chromatic aberration. Here, v3ave ismore preferably greater than 40, further preferably greater than 50,further more preferably greater than 55, and still more preferablygreater than 60.

In addition, in order to appropriately distribute the Abbe numbers,v3ave is preferably less than 80. In this case, an excessive increase inAbbe number of the lens of the third lens group G3 can be suppressed.Thus, in the third lens group G3, it is easy to increase an absolutevalue of the difference between the Abbe number of the positive lens andthe Abbe number of the negative lens, and it is easy to correct theaxial chromatic aberration. Here, v3ave is more preferably less than 75,and further preferably less than 73.

By satisfying Conditional Expression (21), an Abbe number of thepositive lens and an Abbe number of the negative lens constituting thefourth lens group G4 can be appropriately distributed. Thus, it is easyto correct the axial chromatic aberration. More specifically, bysatisfying Conditional Expression (21), a decrease in Abbe number of alens of the fourth lens group G4 can be prevented. Thus, in the fourthlens group G4, it is easy to secure a difference between the Abbe numberof the positive lens and the Abbe number of the negative lens whiledecreasing the absolute value of the difference between the partialdispersion ratio of the positive lens and the partial dispersion ratioof the negative lens. Accordingly, it is easy to correct thesecond-order spectrum of the axial chromatic aberration. Here, v4ave ismore preferably greater than 35, further preferably greater than 40, andfurther more preferably greater than 43.

In addition, in order to appropriately distribute the Abbe numbers,v4ave is preferably less than 80. In this case, an excessive increase inAbbe number of the lens of the fourth lens group G4 can be suppressed.Thus, in the fourth lens group G4, it is easy to increase an absolutevalue of the difference between the Abbe number of the positive lens andthe Abbe number of the negative lens, and it is easy to correct theaxial chromatic aberration. Here, v4ave is more preferably less than 70,and further preferably less than 60.

By satisfying Conditional Expression (22), the Abbe number of thepositive lens of the second lens group G2 can be decreased, and it iseasy to correct the axial chromatic aberration from the visible range tothe SWIR range. Optical glass generally has a tendency such that v isdecreased in a case where θ is decreased. Here, θ2P ave is morepreferably less than 2.05, further preferably less than 2, and furthermore preferably less than 1.9.

In addition, θ2P ave is preferably greater than 1. In this case, it iseasy to decrease the absolute value of the difference between thepartial dispersion ratio of the positive lens and the partial dispersionratio of the negative lens in the second lens group G2, and it is easyto correct the second-order spectrum of the axial chromatic aberration.Here, θ2P ave is more preferably greater than 1.1, and furtherpreferably greater than 1.2.

By satisfying Conditional Expression (23), it is easy to increase theAbbe number of the negative lens of the second lens group G2, and it iseasy to correct the axial chromatic aberration from the visible range tothe SWIR range. Here, θ2N ave is more preferably greater than 1.5, andfurther preferably greater than 1.7.

In addition, θ2N ave is preferably less than 2.3. In this case, it iseasy to use a large number of lenses having a high refractive index asthe negative lens of the second lens group G2, and it is easy to reducethe size of the second lens group G2. Here, θ2N ave is more preferablyless than 2.2, and further preferably less than 2.15.

By satisfying Conditional Expression (24), it is easy to use a largenumber of lenses having a high refractive index as the positive lens ofthe fourth lens group G4, and it is easy to reduce the size of thefourth lens group G4. Here, θ4P ave is more preferably less than 2.1,further preferably less than 2, and further more preferably less than1.95.

In addition, θ4P ave is preferably greater than 1.35. In this case, theAbbe number of the positive lens can be increased, and it is easy tocorrect the chromatic aberration from the visible range to the SWIRrange. Here, θ4P ave is more preferably greater than 1.5, and furtherpreferably greater than 1.6.

Conditional Expression (25) is a conditional expression that ispreferably satisfied in a case where the first lens group G1 has apositive refractive power. By satisfying Conditional Expression (25), itis easy to suppress a decrease in positive refractive power of the firstlens group G1. Thus, it is easy to decrease the total length of the lenssystem. Here, ft/f1 is more preferably greater than 0.5, furtherpreferably greater than 1, further more preferably greater than 1.5, andstill more preferably greater than 2.

In addition, ft/f1 is preferably less than 20. In this case, it is easyto suppress an excessive increase in positive refractive power of thefirst lens group G1. Thus, it is easy to correct various types ofaberration. Here, ft/f1 is more preferably less than 10, furtherpreferably less than 8, and further more preferably less than 6.

Conditional Expression (26) is a conditional expression that ispreferably satisfied in a case where the first lens group G1 has apositive refractive power. By satisfying Conditional Expression (26),the refractive power of the positive lens having the highest refractivepower among the positive lenses of the first lens group G1 can beincreased. Thus, it is easy to reduce the size of the first lens groupG1 and decrease the total length of the lens system. Here, ft/f1Pmax ismore preferably greater than 1.2, further preferably greater than 1.4,and further more preferably greater than 1.6.

In addition, ft/f1Pmax is preferably less than 20. In this case, it ispossible that the refractive power of the positive lens having thehighest refractive power among the positive lenses of the first lensgroup G1 is not excessively increased. Thus, it is easy to suppressvarious types of aberration. Here, ft/f1Pmax is more preferably lessthan 12, and further preferably less than 10.

Conditional Expression (27) is a conditional expression that ispreferably satisfied in a case where the second lens group G2 has anegative refractive power. By satisfying Conditional Expression (27) notto be below a lower limit thereof, it is easy to suppress a decrease innegative refractive power of the second lens group G2. Thus, it is easyto increase an angle of view at the wide angle end. Here, f2/fw is morepreferably greater than −8, further preferably greater than −5, furthermore preferably greater than −3, and still more preferably greater than−2.5.

By satisfying Conditional Expression (27) not to be above an upper limitthereof, it is easy to suppress an excessive increase in negativerefractive power of the second lens group G2, and it is easy to correctvarious types of aberration. Here, f2/fw is more preferably less than−0.2, further preferably less than −0.3, further more preferably lessthan −0.4, and still more preferably less than −0.5.

Conditional Expression (28) is a conditional expression that ispreferably satisfied in a case where the second lens group G2 has anegative refractive power. By satisfying Conditional Expression (28),the refractive power of the negative lens having the highest refractivepower among the negative lenses of the second lens group G2 can beincreased. Thus, it is easy to reduce the size of the second lens groupG2. Here, f2Nmax/fw is more preferably greater than -5, furtherpreferably greater than −4, and further more preferably greater than −3.

In addition, f2Nmax/fw is preferably less than −0.1. In this case, it ispossible that the refractive power of the negative lens having thehighest refractive power among the negative lenses of the second lensgroup G2 is not excessively increased. Thus, it is easy to suppressvarious types of aberration. Here, f2Nmax/fw is more preferably lessthan −0.2, and further preferably less than −0.3.

Conditional Expression (29) is a conditional expression that ispreferably satisfied in a case where the first lens group G1 has apositive refractive power and the second lens group G2 has a negativerefractive power. By satisfying Conditional Expression (29), it is easyto suppress a decrease in negative refractive power of the second lensgroup G2. Thus, it is easy to increase the angle of view at the wideangle end. Here, f1/f2 is more preferably less than −2.5, furtherpreferably less than −3, and further more preferably less than −5.

In addition, f1/f2 is preferably greater than −100. In this case, it iseasy to suppress an excessive decrease in positive refractive power ofthe first lens group G1. Thus, it is easy to correct various types ofaberration, and an advantage for decreasing the total length of the lenssystem is achieved. Here, f1/f2 is more preferably greater than −20, andfurther preferably greater than −12.5.

Conditional Expression (30) is a conditional expression that ispreferably satisfied in a case where the second lens group G2 has anegative refractive power and the third lens group G3 has a positiverefractive power. By satisfying Conditional Expression (30) not to bebelow a lower limit thereof, it is easy to suppress an excessiveincrease in negative refractive power of the second lens group G2. Thus,an advantage for decreasing the total length of the lens system isachieved. Alternatively, it is easy to suppress an excessive decrease inpositive refractive power of the third lens group G3. Thus, an advantagefor decreasing the total length of the lens system is achieved. Here,f3/f2 is more preferably greater than −5, and further preferably greaterthan −3.

By satisfying Conditional Expression (30) not to be above an upper limitthereof, it is easy to suppress a decrease in negative refractive powerof the second lens group G2. Thus, it is easy to increase the angle ofview at the wide angle end. Alternatively, it is easy to suppress anincrease in positive refractive power of the third lens group G3. Thus,it is easy to increase the back focus. Here, f3/f2 is more preferablyless than −0.5, further preferably less than −1, and further morepreferably less than −1.5.

Conditional Expression (31) is a conditional expression that ispreferably satisfied in a case where the lens of the third lens group G3closest to the object side is a positive lens. By satisfying ConditionalExpression (31), it is easy to increase a refractive power of a positivelens of the third lens group G3 closest to the object side, and it iseasy to reduce the size of the third lens group G3. Here, TL/f31 is morepreferably greater than 1, further preferably greater than 1.5, andfurther more preferably greater than 2.

In addition, TL/f31 is preferably less than 100. In this case, it iseasy to suppress an increase in total length of the lens system. Here,TL/f31 is more preferably less than 20, and further preferably less than10.

Conditional Expressions (1-1) to (30-1), (1-2) to (5-2), (25-2), (1-3),and (25-3) below are illustrated as examples of preferred conditionalexpressions obtained by combining the upper limits and the lower limitsdescribed above. Conditional expressions preferably satisfied by thevariable magnification optical system are not limited to the conditionalexpressions described below and include all conditional expressionsobtained by any combination of the preferred lower limits and thepreferred upper limits described above for each conditional expression.

−0.0022<(Bfd−BfIR)/ft<0.005  (1-1)

−0.00125<(Bfd−BfIR)/ft<0.0022  (1-2)

−0.001<(Bfd−BfIR)/ft<0.001  (1-3)

1.3<θ1 ave<2.4  (2-1)

1.6<θ1 ave<2.35  (2-2)

−0.5<θ1P ave−θ1N ave<0.5  (3-1)

−0.4<θ1P ave−θ1N ave<0.4  (3-2)

1.4<θ3 ave<2.3  (4-1)

1.5<θ3 ave<2.2  (4-2)

0.3<ft/TL<20  (5-1)

0.1<ft/TL<8  (5-2)

0.7<θ1 ave/θ2 ave<1.7  (6-1)

0.7<θ3 ave/θ2 ave<2  (7-1)

50<v1 ave<95  (8-1)

1.3<θ4 ave<2.3  (9-1)

1.2<θ2 ave<2.3  (10-1)

1.8<θ1P ave<2.2  (11-1)

1.5<θ1N ave<2.3  (12-1)

−2<θ2P ave−θ2N ave<0  (13-1)

0.05<θ3P ave−θ3N ave<1.5  (14-1)

−1<θ4P ave−θ4N ave<1  (15-1)

20<v1P ave−v1N ave<40  (16-1)

−50<v2P ave−v2N ave<−13  (17-1)

15<v3P ave−v3N ave<65  (18-1)

25<v2 ave<60  (19-1)

30<v3 ave<80  (20-1)

30<v4 ave<80  (21-1)

1<θ2P ave<2.2  (22-1)

1.35<θ2N ave<2.3  (23-1)

1.35<θ4P ave<2.2  (24-1)

0.5<ft/f1<20  (25-1)

2<ft/f1<10  (25-2)

1<ft/f1<8  (25-3)

1<ft/f1Pmax<20  (26-1)

−8<f2fw<−0.2  (27-1)

−10<f2N max/fw<−0.1  (28-1)

−100<f1/f2<−0.5  (29-1)

−10<f3/f2<−0.5  (30-1)

0.3<TL/f31<100  (31-1)

Next, three preferred aspects in which the above configurations andconditional expressions are considered will be described. A first aspectis the variable magnification optical system that consists of, in orderfrom the object side to the image side, the first lens group Gl, thesecond lens group G2, and the subsequent lens group, in which allintervals between adjacent lens groups are changed during zooming, andConditional Expressions (1) and (2) are satisfied. According to thefirst aspect, an advantage for favorable correction of the chromaticaberration in the wavelength range of the visible range to the SWIRrange and maintenance of favorable characteristics is achieved. Inaddition, accordingly, the number of lenses constituting the variablemagnification optical system can be further decreased. Thus, anadvantage for suppressing an increase in size of the lens system isachieved.

A second aspect is the variable magnification optical system thatconsists of, in order from the object side to the image side, the firstlens group G1, the second lens group G2, and the subsequent lens group,in which all intervals between adjacent lens groups are changed duringzooming, and Conditional Expression (1) and Conditional Expression (3)are satisfied. According to the second aspect, an advantage forfavorable correction of the chromatic aberration in the wavelength rangeof the visible range to the SWIR range and maintenance of favorablecharacteristics is achieved. In addition, accordingly, the number oflenses constituting the variable magnification optical system can befurther decreased. Thus, an advantage for suppressing an increase insize of the lens system is achieved.

A third aspect is the variable magnification optical system thatconsists of, consecutively in order from the object side to the imageside, the first lens group G1, the second lens group G2, the third lensgroup G3, and the fourth lens group G4, in which all intervals betweenadjacent lens groups are changed during zooming, and ConditionalExpression (1) and Conditional Expression (4) are satisfied. Accordingto the third aspect, an advantage for favorable correction of thechromatic aberration in the wavelength range of the visible range to theSWIR range, maintenance of favorable characteristics, and suppression ofan increase in size of the lens system is achieved.

The example in FIG. 1 is one example and can be subjected to variousmodifications without departing from the gist of the technology of thepresent disclosure. For example, while the subsequent lens group GR ofthe example in FIG. 1 comprises only two lens groups as lens groups, aconfiguration in which the number and refractive powers of lens groupsconstituting the subsequent lens group GR are different from the exampleillustrated in FIG. 1 is also available. Similarly, the number of lensesconstituting each lens group can be set to a different number from theexample illustrated in FIG. 1 . A fixed lens group and a moving lensgroup during zooming can have different configurations from the exampleillustrated in FIG. 1 . The aperture stop St may be arranged at adifferent position from the example in FIG. 1 . For example, theaperture stop St may be arranged in the third lens group or may bearranged in the fourth lens group.

An example in which the optical member PP including various filters andthe like is arranged between the lens system and the image plane Sim isillustrated in FIG. 1 . However, instead of arranging the optical memberPP between the lens system and the image plane Sim, the optical memberPP may be arranged in any group, or the optical member PP may bearranged between groups. Alternatively, a coating having the same effectas various filters and the like may be applied to a lens surface of anylens.

It is preferable that an anti-reflection coating that preventsreflection of light is applied to a lens surface of each lens. While theanti-reflection coating is preferably configured to reduce reflectancein the entire range of the visible range to the SWIR range, theanti-reflection coating may be configured to reduce reflectance in thevisible range and a part of the SWIR range depending on applications.

The variable magnification optical system may comprise a focusingfunction. Focusing may be performed by moving the entire lens system.Alternatively, focusing may be performed by moving only a part of lensesof the lens system. For example, focusing may be performed by movingonly a part of lenses of the first lens group G1. Alternatively,focusing may be performed using a floating focus method of moving aplurality of lenses such that an interval between each other is changedduring focusing.

The variable magnification optical system may comprise a vibration-prooffunction. Vibration proofing may be performed by moving a specific lensgroup. Alternatively, vibration proofing may be performed by moving onlya part of lenses of the lens group. For example, vibration proofing maybe performed by moving only a part of lenses or all lenses of the firstlens group G1, or vibration proofing may be performed by moving only apart of lenses or all lenses of the fourth lens group G4.

The above preferred configurations and available configurationsincluding configurations related to the conditional expressions can beused in any combination thereof and are preferably appropriatelyselectively employed depending on required specifications. According tothe variable magnification optical system of the embodiment of thepresent disclosure, it is possible to implement favorablecharacteristics by correcting the chromatic aberration in the wavelengthrange of the visible range to the SWIR range while suppressing anincrease in size of the lens system.

Next, examples of the variable magnification optical system according tothe embodiment of the present disclosure will be described.

EXAMPLE 1

A cross-sectional view of a configuration of the variable magnificationoptical system of Example 1 is illustrated in FIG. 1 , and anillustration method thereof is described above. Thus, duplicatedescriptions will be partially omitted here. The variable magnificationoptical system of Example 1 is a zoom lens that consists of, in orderfrom the object side to the image side, the first lens group G1 having apositive refractive power, the second lens group G2 having a negativerefractive power, the third lens group G3 having a positive refractivepower, the aperture stop St, and the fourth lens group G4 having apositive refractive power. During zooming, the first lens group G1, theaperture stop St, and the fourth lens group G4 are fixed with respect tothe image plane Sim, and the second lens group G2 and the third lensgroup G3 are moved along the optical axis Z by changing an intervalbetween each other. The first lens group G1 consists of the lenses L11to L15. The second lens group G2 consists of the lenses L21 to L25. Thethird lens group G3 consists of the lenses L31 to L34. The fourth lensgroup G4 consists of the lenses L41 to L57.

For the variable magnification optical system of Example 1, basic lensdata is shown in Table 1A and Table 1B, specifications and a variablesurface interval are shown in Table 2, and various data are shown inTable 3 and Table 4. The basic lens data is separately shown in twotables of Table 1A and Table 1B in order to avoid one lengthy table.Table 1A shows the first lens group G1, the second lens group G2, andthe third lens group G3. Table 1B shows the aperture stop St, the fourthlens group G4, and the optical member PP.

In Table 1A and Table 1B, a field of Sn shows a surface number in a casewhere the number is increased by one in a direction of the image sidefrom a first surface denoting a surface closest to the object side. Afield of R shows a radius of curvature of each surface. A field of Dshows a surface interval on the optical axis between each surface and asurface adjacent thereto on the image side. A field of nd shows a d-linerefractive index of each constituent. A field of v shows a d line-basedAbbe number of each constituent. A field of material shows a materialname of each constituent. All materials shown in Table 1A and Table 1Bare manufactured by OHARA INC.

In Table 1A and Table 1B, a sign of a radius of curvature of a surfacehaving a shape of a convex surface toward the object side is positive,and a sign of a radius of curvature of a surface having a surface of aconvex surface toward the image side is negative. In Table 1A, a symbolDD[ ] is used for the variable surface interval during zooming and iswritten in the field of D by writing a surface number on the object sideof this interval in [ ]. In Table 1B, a surface number and a word (St)are written in the field of a surface number of a surface correspondingto the aperture stop St. A value in the lowermost field of D in Table 1Bis an interval between a surface closest to the image side in the tableand the image plane Sim.

Table 2 shows a magnification Zr, a focal length f, an F number FNo.,and a maximum total angle of view 2ω as the specifications. In a fieldof 2ω, (°) means a unit of degrees. In addition, Table 2 shows thevariable surface interval during zooming. In Table 2, values of the wideangle end state, the middle focal length state, and the telephoto endstate are shown in fields of WIDE, MIDDLE, and TELE, respectively.

Table 3 shows TL, f1, f2, f3, and f31 used in the above conditionalexpressions and a focal length f4 of the fourth lens group G4. Valuesshown in Table 1A, Table 1B, Table 2, and Table 3 are d-line data in astate where the object at infinity is focused.

Table 4 shows a back focus in each wavelength. In Table 4, Bfd is thed-line back focus in the air-conversion distance of the entire system atthe telephoto end. In a left field of Table 4, a numerical value after“Bf_” is a wavelength in units of nanometers (nm), and “Bf_numericalvalue” means the back focus in the wavelength of the numerical value inthe air-conversion distance of the entire system at the telephoto end. Avalue of the corresponding back focus is shown in a right field in unitsof millimeters (mm).

In the data of each table, unless otherwise specified, degree is used asa unit of angle, and millimeter (mm) is used as a unit of length.However, since the optical system can be used by proportionallyenlarging or proportionally reducing the optical system, otherappropriate units can also be used. In each table shown below, numericalvalues rounded to a predetermined digit are written.

TABLE 1A Example 1 Sn R D nd ν Material 1 166.0458 4.0000 1.51633 64.14S-BSL7 2 112.9379 21.0000  1.49700 81.54 S-FPL51 3 −312.9580 1.0000 4142.3417 15.0000  1.49700 81.54 S-FPL51 5 −242.3717 4.0000 1.79952 42.22S-LAH52 6 195.9686 5.0000 7 119.7940 12.0000  1.49700 81.54 S-FPL51 8411.8138 DD[8]  9 82.4139 5.0000 1.96300 24.11 S-TIH57 10 −59.23782.0100 1.80610 40.93 S-LAH53V 11 24.0543 5.0000 12 −28.6661 4.00001.71300 53.87 S-LAL8 13 −86.4771 2.0000 14 −32.6016 7.0000 1.67270 32.10S-TIM25 15 −20.7725 1.5100 1.60311 60.64 S-BSM14 16 −57.4517 DD[16] 17251.1119 4.0000 1.49700 81.54 S-FPL51 18 −96.3510 0.2000 19 43.08484.0000 1.49700 81.54 S-FPL51 20 3803.5690 0.5000 21 117.0905 1.12111.80400 46.58 S-LAH65V 22 26.9661 5.8211 1.53775 74.70 S-FPM3 231164.6058 DD[23]

TABLE 1B Example 1 Sn R D nd ν Material 24 (St) ∞ 3.0532 25 118.90115.0000 1.74400 44.79 S-LAM2 26 −59.1209 1.0000 27 −29.7531 1.00001.83400 37.21 S-LAH60V 28 147.8947 4.0100 1.51742 52.43 S-NSL36 29−24.5000 0.2000 30 −103.8858 1.0000 1.69680 55.53 S-LAL14 31 67.62863.6522 32 −166.1516 1.0000 1.69680 55.53 S-LAL14 33 78.1349 0.2000 3420.0226 4.6950 1.80000 29.84 S-NBH55 35 42.1333 1.0000 36 89.2272 1.77641.60300 65.44 S-PHM53 37 21.5538 1.5000 38 67.3255 3.0465 1.65412 39.68S-NBH5 39 −60.5367 0.1000 40 21.0488 4.0000 1.54814 45.78 S-TIL1 41−26.3658 1.0000 1.85478 24.80 S-NBH56 42 140.1678 2.0000 43 −41.88391.0000 1.78800 47.37 S-LAH64 44 23.4749 3.7239 1.80610 40.93 S-LAH53V 4543.5903 2.0000 46 −56.0501 2.5430 1.72916 54.09 S-LAL19 47 37.81535.0100 1.60562 43.71 S-BAM4 48 −22.8814 28.6055 49 56.7814 5.09901.80000 29.84 S-NBH55 50 124.8251 0.7000 51 54.1871 5.5415 1.51742 52.43S-NSL36 52 −22.1912 2.0000 1.85478 24.80 S-NBH56 53 −178.1521 6.0000 54∞ 1.0000 1.51633 64.14 S-BSL7 55 ∞ 7.6537

TABLE 2 Example 1 WIDE MIDDLE TELE Zr 1.0 6.2 38.0 f 20.5 126.5 780.1FNo. 4.20 5.03 8.30 ω (°) 14.9 2.4 0.4 DD[8] 2.7897 70.6841 93.6903DD[16] 178.4195 82.3754 3.0468 DD[23] 5.3470 33.4967 89.8191

TABLE 3 Example 1 TL 400.5 f1 175.0 f2 −26.0 f3 65.0 f4 316.3 f31 140.6

TABLE 4 Example 1 Bfd 14.31 Bf_1300 14.60 Bf_1426 14.71 Bf_1450 14.72Bf_1450 14.72 Bf_1460 14.73 Bf_1530 14.77 Bf_1550 14.78 Bf_1570 14.79Bf_1651 14.81 Bf_1653 14.81 Bf_1696 14.80 Bf_1725 14.80 Bf_1750 14.79Bf_1870 14.71 Bf_1940 14.63 Bf_1970 14.59 Bf_2050 14.44 Bf_2120 14.27Bf_2325 13.53

FIG. 3 illustrates each aberration diagram of the variable magnificationoptical system of Example 1 in a state where the object at infinity isfocused. In FIG. 3 , spherical aberration, astigmatism, distortion, andlateral chromatic aberration are shown in order from the left. In FIG. 3, aberration in the wide angle end state is illustrated in an upper partdenoted by “WIDE”. Aberration in the middle focal length state isillustrated in a middle part denoted by “MIDDLE”. Aberration in thetelephoto end state is illustrated in a lower part denoted by “TELE”. Inthe spherical aberration diagram, aberration in d line, C line, F line,g line, t line, a wavelength of 1530 nm, a wavelength of 1970 nm, and awavelength of 2325 nm are illustrated by a solid line, a long brokenline, a short broken line, a narrow long-dashed line, a dotted line, athick short-dashed line, a double-dashed line, and a thick long brokenline, respectively. In the astigmatism diagram, d-line aberration in asagittal direction is illustrated by a solid line, and d-line aberrationin a tangential direction is illustrated by a long broken line. In thedistortion diagram, d-line aberration is illustrated by a solid line. Inthe lateral chromatic aberration diagram, aberration in C line, F line,g line, t line, a wavelength of 1530 nm, a wavelength of 1970 nm, and awavelength of 2325 nm are illustrated by a long broken line, a shortbroken line, a narrow long-dashed line, a dotted line, a thickshort-dashed line, a double-dashed line, and a thick long broken line,respectively. In the spherical aberration diagram, FNo. means the Fnumber. In the other aberration diagrams, ω means a half angle of view.

Symbols, meanings, writing methods, and illustration methods of eachdata related to Example 1 are the same in the following examples unlessotherwise specified. Thus, duplicate descriptions will be omitted below.

EXAMPLE 2

A configuration of a variable magnification optical system of Example 2and a movement trajectory are illustrated in FIG. 4 . The variablemagnification optical system of Example 2 consists of, in order from theobject side to the image side, the first lens group G1 having a positiverefractive power, the second lens group G2 having a negative refractivepower, the third lens group G3 having a positive refractive power, theaperture stop St, and the fourth lens group G4 having a negativerefractive power. During zooming, the first lens group G1, the aperturestop St, and the fourth lens group G4 are fixed with respect to theimage plane Sim, and the second lens group G2 and the third lens groupG3 are moved along the optical axis Z by changing an interval betweeneach other. The first lens group G1 consists of lenses L11 to L16. Thesecond lens group G2 consists of lenses L21 to L27. The third lens groupG3 consists of lenses L31 to L36. The fourth lens group G4 consists oflenses L41 to L50. For the variable magnification optical system ofExample 2, basic lens data is shown in Table 5A and Table 5B, andspecifications and a variable surface interval are shown in Table 6.Various data are shown in Table 7 and Table 8, and each aberrationdiagram is illustrated in FIG. 5 . All materials shown in Table 5A andTable 5B are manufactured by OHARA INC.

TABLE 5A Example 2 Sn R D nd ν Material 1 262.6800 22.0000  1.4387594.94 S-FPL53 2 −346.4618 2.0000 3 −362.4394 3.0000 1.51633 64.14 S-BSL74 1520.2617 1.0000 5 474.9879 10.0000  1.61800 63.33 S-PHM52 6 882.95860.5000 7 334.8998 1.5000 1.70154 41.24 S-BAH27 8 139.8976 18.0000 1.43875 94.94 S-FPL53 9 1891.3228 0.5000 10 164.5283 13.9776  1.4387594.94 S-FPL53 11 1210.3325 DD[11] 12 −140.4581 1.0000 1.56384 60.67S-BAL41 13 188.5298 2.2000 14 98.1201 1.0000 1.58913 61.13 S-BAL35 1577.5904 3.5000 16 −242.2980 3.0000 1.92286 18.90 S-NPH2 17 −53.75261.5000 1.54814 45.78 S-TIL1 18 173.2388 2.0000 19 −113.3766 1.00001.49700 81.54 S-FPL51 20 28.4989 8.0000 1.51633 64.14 S-BSL7 21 86.96862.5000 22 −119.3128 2.0000 1.74100 52.64 S-LAL61 23 367.1919 DD[23] 2489.6955 4.8214 1.43875 94.94 S-FPL53 25 −107.4861 0.1202 26 59.70891.0000 1.90366 31.34 S-LAH95 27 51.6163 4.5000 1.43875 94.94 S-FPL53 28−518.2264 0.1200 29 184.9380 3.0000 1.69680 55.53 S-LAL14 30 46.03422.0000 31 59.2152 7.0000 1.63854 55.38 S-BSM18 32 −44.5143 2.00001.72000 41.98 S-LAM58 33 1477.9789 DD[33]

TABLE 5B Example 2 Sn R D nd ν Material 34 (St) ∞ 2.1937 35 113.85890.6000 1.88300 40.76 S-LAH58 36 52.6534 3.0000 1.74000 28.30 S-TIH3 37204.8380 1.0000 38 34.9439 0.8000 1.65100 56.16 S-LAL54 39 38.81280.5000 40 25.3979 3.5100 1.43875 94.94 S-FPL53 41 −77.8040 0.80001.71300 53.87 S-LAL8 42 30.2211 32.6140 43 49.3977 3.0000 1.67270 32.10S-TIM25 44 −28.9922 0.1000 45 283.1228 3.0000 1.48749 70.24 S-FSL5 46−18.8563 1.0000 1.88300 40.76 S-LAH58 47 −92.9167 3.0000 48 298.25090.8000 1.75500 52.32 S-YGH51 49 9.8855 3.0000 1.43875 94.94 S-FPL53 5056.8278 5.0000 51 ∞ 1.2000 1.51633 64.14 S-BSL7 52 ∞ 18.8081

TABLE 6 Example 2 WIDE MIDDLE TELE Zr 1.0 7.6 57.0 f 17.3 130.9 988.3FNo. 3.60 4.51 7.62 ω (°) 17.8 2.3 0.3 DD[11] 9.4493 126.6970 163.4178DD[23] 258.7170 109.8837 3.1512 DD[33] 2.9649 34.5504 104.5621

TABLE 7 Example 2 TL 479.4 f1 255.2 f2 −33.8 f3 74.4 f4 −128.2 f31 112.3

TABLE 8 Example 2 Bfd 24.60 Bf_1300 24.83 Bf_1426 24.91 Bf_1450 24.92Bf_1450 24.92 Bf_1460 24.92 Bf_1530 24.95 Bf_1550 24.95 Bf_1570 24.95Bf_1651 24.95 Bf_1653 24.95 Bf_1696 24.94 Bf_1725 24.93 Bf_1750 24.91Bf_1870 24.81 Bf_1940 24.71 Bf_1970 24.66 Bf_2050 24.50 Bf_2120 24.33Bf_2325 23.61

EXAMPLE 3

A configuration of a variable magnification optical system of Example 3and a movement trajectory are illustrated in FIG. 6 . The variablemagnification optical system of Example 3 consists of, in order from theobject side to the image side, the first lens group G1 having a positiverefractive power, the second lens group G2 having a negative refractivepower, the third lens group G3 having a positive refractive power, theaperture stop St, and the fourth lens group G4 having a negativerefractive power. During zooming, the first lens group G1, the aperturestop St, and the fourth lens group G4 are fixed with respect to theimage plane Sim, and the second lens group G2 and the third lens groupG3 are moved along the optical axis Z by changing an interval betweeneach other. The first lens group G1 consists of the lenses L11 to L16.The second lens group G2 consists of the lenses L21 to L27. The thirdlens group G3 consists of the lenses L31 to L36. The fourth lens groupG4 consists of lenses L41 to L51. For the variable magnification opticalsystem of Example 3, basic lens data is shown in Table 9A and Table 9B,and specifications and a variable surface interval are shown in Table10. Various data are shown in Table 11 and Table 12, and each aberrationdiagram is illustrated in FIG. 7 . All materials shown in Table 9A andTable 9B are manufactured by OHARA INC.

TABLE 9A Example 3 Sn R D nd ν Material 1 238.3732 22.0000  1.4387594.94 S-FPL53 2 −161.2457 4.0000 3 −155.4722 3.0000 1.51633 64.14 S-BSL74 1036.2284 2.0000 5 184.5109 12.0000  1.69680 55.53 S-LAL14 6 2243.97020.5000 7 398.9216 1.5000 1.67003 47.23 S-BAH10 8 101.2520 18.0000 1.43875 94.94 S-FPL53 9 319.2713 0.5000 10 121.6904 12.0000  1.4387594.94 S-FPL53 11 153.3566 DD[11] 12 163.9393 4.0000 1.67790 55.34S-LAL12 13 −181.8297 1.0000 14 152.1124 1.0000 1.58913 61.13 S-BAL35 15102.2663 3.0000 16 150.9846 3.0000 1.92286 18.90 S-NPH2 17 −199.48821.5000 1.54814 45.78 S-TIL1 18 85.3113 3.0000 19 −113.7129 1.00001.49700 81.54 S-FPL51 20 51.2189 5.0000 1.51633 64.14 S-BSL7 21 25.19685.0000 22 −32.5218 2.0000 1.74100 52.64 S-LAL61 23 −97.8041 DD[23] 2468.4997 4.8214 1.43875 94.94 S-FPL53 25 −115.5670 0.1202 26 85.64501.0000 1.90366 31.34 S-LAH95 27 38.8286 4.5000 1.43875 94.94 S-FPL53 28−151.9851 0.1200 29 84.8198 3.0000 1.69680 55.53 S-LAL14 30 147.06202.0000 31 −4008.0448 1.0000 1.63854 55.38 S-BSM18 32 33.4654 5.00001.72000 41.98 S-LAM58 33 231.1693 DD[33]

TABLE 9B Example 3 Sn R D nd ν Material 34 (St) 2.1937 35 107.01010.6000 1.88300 40.76 S-LAH58 36 35.2650 3.0000 1.74000 28.30 S-TIH3 37226.4375 1.0000 38 39.0957 0.8000 1.65100 56.16 S-LAL54 39 34.71350.5000 40 22.1005 3.5100 1.43875 94.94 S-FPL53 41 −84.1553 0.80001.71300 53.87 S-LAL8 42 30.1678 38.3445 43 71.0745 2.5000 1.67270 32.10S-TIM25 44 −34.7544 0.1000 45 2066.7097 2.5000 1.48749 70.24 S-FSL5 46−21.1670 1.0000 1.88300 40.76 S-LAH58 47 −99.1392 0.5000 48 15.16321.0000 1.71300 53.87 S-LAL8 49 11.5637 1.5000 50 84.7449 0.8000 1.7550052.32 S-YGH51 51 20.6994 3.0000 1.43875 94.94 S-FPL53 52 47.2681 5.000053 ∞ 1.2000 1.51633 64.14 S-BSL7 54 ∞ 18.3942

TABLE 10 Example 3 WIDE MIDDLE TELE Zr 1.0 7.6 57.0 f 26.0 196.5 1483.3FNo. 4.09 5.34 12.51 ω (°) 11.4 1.6 0.2 DD[11] 17.7462 139.2476 178.2565DD[23] 257.9358 107.5640 2.6487 DD[33] 9.1484 38.0188 103.9252

TABLE 11 Example 3 TL 499.4 f1 313.7 f2 −35.3 f3 69.4 f4 −72.7 f31 98.8

TABLE 12 Example 3 Bfd 24.19 Bf_1300 24.38 Bf_1426 24.52 Bf_1450 24.54Bf_1450 24.54 Bf_1460 24.54 Bf_1530 24.59 Bf_1550 24.60 Bf_1570 24.60Bf_1651 24.61 Bf_1653 24.61 Bf_1696 24.60 Bf_1725 24.59 Bf_1750 24.57Bf_1870 24.44 Bf_1940 24.31 Bf_1970 24.25 Bf_2050 24.03 Bf_2120 23.80Bf_2325 22.81

EXAMPLE 4

A configuration of a variable magnification optical system of Example 4and a movement trajectory are illustrated in FIG. 8 . The variablemagnification optical system of Example 4 consists of, in order from theobject side to the image side, the first lens group G1 having a positiverefractive power, the second lens group G2 having a negative refractivepower, the third lens group G3 having a positive refractive power, theaperture stop St, and the fourth lens group G4 having a negativerefractive power. During zooming, the first lens group G1, the aperturestop St, and the fourth lens group G4 are fixed with respect to theimage plane Sim, and the second lens group G2 and the third lens groupG3 are moved along the optical axis Z by changing an interval betweeneach other. The first lens group G1 consists of the lenses L11 to L16.The second lens group G2 consists of the lenses L21 to L27. The thirdlens group G3 consists of the lenses L31 to L36. The fourth lens groupG4 consists of the lenses L41 to L51. For the variable magnificationoptical system of Example 4, basic lens data is shown in Table 13A andTable 13B, and specifications and a variable surface interval are shownin Table 14. Various data are shown in Table 15 and Table 16, and eachaberration diagram is illustrated in FIG. 9 . All materials shown inTable 13A and Table 13B are manufactured by OHARA INC.

TABLE 13A Example 4 Sn R D nd ν Material 1 354.4124 28.0000  1.4387594.94 S-FPL53 2 −198.7344 3.0000 3 −198.9426 2.0000 1.53996 59.46S-BAL12 4 170.6499 23.0000  1.43875 94.94 S-FPL53 5 −1489.7161 0.5000 6220.0292 14.0000  1.61800 63.33 S-PHM52 7 1102.0610 0.5000 8 184.39611.5000 1.67003 47.23 S-BAH10 9 141.3399 16.0000  1.43875 94.94 S-FPL5310 334.3144 DD[10] 11 57.5771 7.0000 1.77250 49.60 S-LAH66 12 338.34251.5000 13 93.3552 1.0000 1.51633 64.14 S-BSL7 14 30.0525 6.5000 15280.1305 3.0000 1.92286 18.90 S-NPH2 16 −212.7253 1.5000 1.51742 52.43S-NSL36 17 42.3543 1.5000 18 39.4746 1.0000 1.49700 81.54 S-FPL51 1916.1131 6.5000 1.51633 64.14 S-BSL7 20 45.4957 4.0000 21 −57.3257 1.50001.88300 40.76 S-LAH58 22 61.2044 DD[22] 23 58.2651 4.8214 1.43875 94.94S-FPL53 24 −205.4930 0.1202 25 77.7181 1.0000 1.90366 31.34 S-LAH95 2641.6050 5.0000 1.43875 94.94 S-FPL53 27 −135.2612 0.1200 28 80.42243.0000 1.69680 55.53 S-LAL14 29 −279.5500 1.5000 30 −141.8574 1.00001.69100 54.82 S-LAL9 31 22.3833 8.0000 1.67003 47.23 S-BAH10 32 275.8818DD[32]

TABLE 13B Example 4 Sn R D nd ν Material 33 (St) ∞ 2.1937 34 216.69160.6000 1.88300 40.76 S-LAH58 35 35.8329 3.0000 1.78470 26.29 S-TIH23 36242.3271 1.0000 37 41.3933 0.8000 1.65160 58.55 S-LAL7 38 32.5808 0.020039 21.6789 4.0100 1.43875 94.94 S-FPL53 40 −35.7917 0.8000 1.77250 49.60S-LAH66 41 31.8185 22.1788 42 33.7876 3.0000 1.67270 32.10 S-TIM25 43−31.3415 0.1000 44 165.1396 3.0000 1.48749 70.24 S-FSL5 45 −18.79411.0000 1.88300 40.76 S-LAH58 46 −64.5585 0.0200 47 14.2943 0.80001.74100 52.64 S-LAL61 48 10.3719 2.0000 49 −35.1290 0.8000 1.80400 46.53S-LAH65VS 50 24.0596 2.5000 1.43875 94.94 S-FPL53 51 −23.3141 5.0000 52∞ 1.2000 1.51633 64.14 S-BSL7 53 ∞ 29.6299

TABLE 14 Example 4 WIDE MIDDLE TELE Zr 1.0 7.6 57.0 f 26.0 196.3 1482.2FNo. 4.00 4.82 9.93 ω (°) 11.1 1.6 0.2 DD[10] 20.0109 135.6393 173.4997DD[22] 236.1068 96.1321 1.3915 DD[32] 11.7659 36.1121 92.9923

TABLE 15 Example 4 TL 499.2 f1 295.9 f2 −33.5 f3 60.1 f4 −97.2 f31 104.0

TABLE 16 Example 4 Bfd 35.42 Bf_1300 35.71 Bf_1426 35.80 Bf_1450 35.80Bf_1450 35.80 Bf_1460 35.81 Bf_1530 35.82 Bf_1550 35.82 Bf_1570 35.82Bf_1651 35.78 Bf_1653 35.78 Bf_1696 35.75 Bf_1725 35.72 Bf_1750 35.69Bf_1870 35.49 Bf_1940 35.32 Bf_1970 35.23 Bf_2050 34.97 Bf_2120 34.68Bf_2325 33.53

EXAMPLE 5

A configuration of a variable magnification optical system of Example 5and a movement trajectory are illustrated in FIG. 10 . The variablemagnification optical system of Example 5 consists of, in order from theobject side to the image side, the first lens group G1 having a positiverefractive power, the second lens group G2 having a negative refractivepower, the third lens group G3 having a positive refractive power, theaperture stop St, and the fourth lens group G4 having a negativerefractive power. During zooming, the first lens group G1, the aperturestop St, and the fourth lens group G4 are fixed with respect to theimage plane Sim, and the second lens group G2 and the third lens groupG3 are moved along the optical axis Z by changing an interval betweeneach other. The first lens group G1 consists of the lenses L11 to L15.The second lens group G2 consists of the lenses L21 to L27. The thirdlens group G3 consists of the lenses L31 to L36. The fourth lens groupG4 consists of the lenses L41 to L49. For the variable magnificationoptical system of Example 5, basic lens data is shown in Table 17A andTable 17B, and specifications and a variable surface interval are shownin Table 18. Various data are shown in Table 19 and Table 20, and eachaberration diagram is illustrated in FIG. 11 . All materials shown inTable 17A and Table 17B are manufactured by OHARA INC.

TABLE 17A Example 5 Sn R D nd ν Material 1 285.3397 26.0000  1.4387594.94 S-FPL53 2 −271.1864 3.0000 3 −276.7274 1.5000 1.53996 59.46S-BAL12 4 173.0361 22.0000  1.43875 94.94 S-FPL53 5 −1754.0451 0.5000 6294.4781 15.0000  1.61800 63.33 S-PHM52 7 640.1696 2.0000 8 227.002918.0000  1.43875 94.94 S-FPL53 9 295.0200 DD[9]  10 53.1029 6.00001.77250 49.60 S-LAH66 11 291.2663 1.0000 12 63.3709 1.0000 1.51633 64.14S-BSL7 13 31.6812 6.0000 14 279.0751 3.0000 1.92286 18.90 S-NPH2 15−389.6594 1.5000 1.51742 52.43 S-NSL36 16 38.3318 1.5000 17 42.33857.0000 1.51633 64.14 S-BSL7 18 −41.9571 1.0000 1.49700 81.54 S-FPL51 1955.7579 4.0000 20 −65.3713 1.5000 1.88300 40.76 S-LAH58 21 58.9574DD[21] 22 55.0159 6.0000 1.43875 94.94 S-FPL53 23 −90.8292 0.1202 2447.4574 1.0000 1.90366 31.34 S-LAH95 25 34.9737 6.0000 1.43875 94.94S-FPL53 26 −129.9230 0.1200 27 68.7785 3.0000 1.69680 55.53 S-LAL14 28838.8993 1.5000 29 −99.2717 1.0000 1.69100 54.82 S-LAL9 30 25.15576.0000 1.67003 47.23 S-BAH10 31 76.5115 DD[31]

TABLE 17B Example 5 Sn R D nd ν Material 32 (St) ∞ 2.1937 33 232.50010.6000 1.88300 40.76 S-LAH58 34 39.6194 3.0000 1.78470 26.29 S-TIH23 35103.5188 1.0000 36 40.9441 0.8000 1.65160 58.55 S-LAL7 37 29.8330 0.500038 22.1999 4.0100 1.43875 94.94 S-FPL53 39 −52.2056 0.8000 1.77250 49.60S-LAH66 40 47.9704 24.4259 41 22.0685 3.0000 1.67270 32.10 S-TIM25 42−40.2132 0.1000 43 −99.3795 3.0000 1.48749 70.24 S-FSL5 44 −18.79071.0000 1.88300 40.76 S-LAH58 45 −57.0760 0.0200 46 84.0523 0.80001.74100 52.64 S-LAL61 47 12.1765 4.0486 48 ∞ 1.2000 1.51633 64.14 S-BSL749 ∞ 36.3965

TABLE 18 Example 5 WIDE MIDDLE TELE Zr 1.0 5.5 30.0 f 65.0 355.8 1948.7FNo. 5.04 6.50 13.24 ω (°) 4.6 0.9 0.2 DD[9] 99.5957 200.6130 241.8335DD[21] 208.6796 87.2769 1.6880 DD[31] 7.8576 28.2431 72.6114

TABLE 19 Example 5 TL 548.9 f1 401.4 f2 −41.9 f3 56.9 f4 −38.7 f31 79.1

TABLE 20 Example 5 Bfd 41.24 Bf_1300 41.69 Bf_1426 41.81 Bf_1450 41.82Bf_1450 41.82 Bf_1460 41.82 Bf_1530 41.84 Bf_1550 41.84 Bf_1570 41.84Bf_1651 41.80 Bf_1653 41.80 Bf_1696 41.76 Bf_1725 41.72 Bf_1750 41.69Bf_1870 41.43 Bf_1940 41.21 Bf_1970 41.10 Bf_2050 40.75 Bf_2120 40.39Bf_2325 38.93

EXAMPLE 6

A configuration of a variable magnification optical system of Example 6and a movement trajectory are illustrated in FIG. 12 . The variablemagnification optical system of Example 6 consists of, in order from theobject side to the image side, the first lens group G1 having a positiverefractive power, the second lens group G2 having a negative refractivepower, the third lens group G3 having a positive refractive power, theaperture stop St, and the fourth lens group G4 having a negativerefractive power. During zooming, the first lens group G1, the aperturestop St, and the fourth lens group G4 are fixed with respect to theimage plane Sim, and the second lens group G2 and the third lens groupG3 are moved along the optical axis Z by changing an interval betweeneach other. The first lens group G1 consists of the lenses L11 to L15.The second lens group G2 consists of the lenses L21 to L27. The thirdlens group G3 consists of the lenses L31 to L36. The fourth lens groupG4 consists of the lenses L41 to L51. For the variable magnificationoptical system of Example 6, basic lens data is shown in Table 21A andTable 21B, and specifications and a variable surface interval are shownin Table 22. Various data are shown in Table 23 and Table 24, and eachaberration diagram is illustrated in FIG. 13 . All materials shown inTable 21A and Table 21B are manufactured by OHARA INC.

TABLE 21A Example 6 Sn R D nd ν Material 1 264.5194 27.0000  1.4387594.94 S-FPL53 2 −250.2853 3.0000 3 −251.6786 1.5000 1.53996 59.46S-BAL12 4 162.2748 20.0000  1.43875 94.94 S-FPL53 5 −3374.8099 0.5000 6249.7240 15.0000  1.61800 63.33 S-PHM52 7 535.8382 2.0000 8 238.163715.0000  1.43875 94.94 S-FPL53 9 295.0791 DD[9]  10 56.3269 7.00001.77250 49.60 S-LAH66 11 1021.3101 1.0000 12 85.3713 1.0000 1.5163364.14 S-BSL7 13 32.3783 6.0000 14 295.7935 3.0000 1.92286 18.90 S-NPH215 −368.9432 1.5000 1.51742 52.43 S-NSL36 16 43.5365 1.5000 17 49.94171.0000 1.49700 81.54 S-FPL51 18 16.6525 9.0000 1.51633 64.14 S-BSL7 1988.3843 4.0000 20 −55.1887 2.0000 1.88300 40.76 S-LAH58 21 55.5032DD[21] 22 53.6069 4.8214 1.43875 94.94 S-FPL53 23 −209.3065 0.1202 2459.6751 1.0000 1.90366 31.34 S-LAH95 25 35.4842 6.0000 1.43875 94.94S-FPL53 26 −146.6139 0.1200 27 75.1191 3.0000 1.69680 55.53 S-LAL14 28586.1434 1.5000 29 −190.2983 1.0000 1.69100 54.82 S-LAL9 30 22.22607.0000 1.67003 47.23 S-BAH10 31 303.6294 DD[31]

TABLE 21B Example 6 Sn R D nd ν Material 32 (St) ∞ 2.1937 33 91.44570.6000 1.88300 40.76 S-LAH58 34 71.4219 3.0000 1.78470 26.29 S-TIH23 35167.9605 1.0000 36 36.6878 0.8000 1.65160 58.55 S-LAL7 37 31.0475 1.000038 35.4957 4.0100 1.43875 94.94 S-FPL53 39 −53.9402 0.8000 1.77250 49.60S-LAH66 40 43.8164 23.0881 41 26.3851 3.0000 1.67270 32.10 S-TIM25 42−43.5851 0.1000 43 −193.9217 3.0000 1.48749 70.24 S-FSL5 44 −19.07471.0000 1.88300 40.76 S-LAH58 45 −50.1084 0.5000 46 41.1985 0.80001.74100 52.64 S-LAL61 47 11.4276 2.0000 48 −41.2045 0.8000 1.80400 46.53S-LAH65VS 49 −50.5723 2.5000 1.43875 94.94 S-FPL53 50 −495.6157 5.000051 ∞ 1.2000 1.51633 64.14 S-BSL7 52 ∞ 36.1575

TABLE 22 Example 6 WIDE MIDDLE TELE Zr 1.0 5.5 30.0 f 65.2 357.2 1956.8FNo. 5.10 6.47 13.25 ω (°) 4.6 0.9 0.2 DD[9] 98.9661 199.3827 240.0178DD[21] 209.1510 87.6268 1.6258 DD[31] 3.0347 24.1423 69.5083

TABLE 23 Example 6 TL 548.9 f1 400.8 f2 −41.0 f3 58.7 f4 −37.2 f31 97.8

TABLE 24 Example 6 Bfd 41.95 Bf_1300 42.43 Bf_1426 42.54 Bf_1450 42.55Bf_1450 42.55 Bf_1460 42.56 Bf_1530 42.58 Bf_1550 42.57 Bf_1570 42.57Bf_1651 42.53 Bf_1653 42.53 Bf_1696 42.48 Bf_1725 42.44 Bf_1750 42.41Bf_1870 42.14 Bf_1940 41.91 Bf_1970 41.80 Bf_2050 41.44 Bf_2120 41.07Bf_2325 39.57

EXAMPLE 7

A configuration of a variable magnification optical system of Example 7and a movement trajectory are illustrated in FIG. 14 . The variablemagnification optical system of Example 7 consists of, in order from theobject side to the image side, the first lens group G1 having a positiverefractive power, the second lens group G2 having a negative refractivepower, the third lens group G3 having a positive refractive power, theaperture stop St, and the fourth lens group G4 having a negativerefractive power. During zooming, the first lens group G1, the aperturestop St, and the fourth lens group G4 are fixed with respect to theimage plane Sim, and the second lens group G2 and the third lens groupG3 are moved along the optical axis Z by changing an interval betweeneach other. The first lens group G1 consists of the lenses L11 to L16.The second lens group G2 consists of the lenses L21 to L25. The thirdlens group G3 consists of the lenses L31 to L36. The fourth lens groupG4 consists of the lenses L41 to L50. For the variable magnificationoptical system of Example 7, basic lens data is shown in Table 25A andTable 25B, and specifications and a variable surface interval are shownin Table 26. Various data are shown in Table 27 and Table 28, and eachaberration diagram is illustrated in FIG. 15 . All materials shown inTable 25A and Table 25B are manufactured by OHARA INC.

TABLE 25A Example 7 Sn R D nd ν Material 1 327.7181 3.0000 1.51633 64.14S-BSL7 2 219.9715 40.0000 1.43875 94.94 S-FPL53 3 −461.8678 2.0000 4449.0015 1.5000 1.51633 64.14 S-BSL7 5 272.6623 24.0000 1.43875 94.94S-FPL53 6 −1642.4371 14.0000 7 −469.8335 10.0000 1.67003 47.23 S-BAH10 81686.1997 1.0000 9 179.5434 15.0000 1.43875 94.94 S-FPL53 10 199.7426DD[10] 11 631.0258 4.0000 1.92286 18.90 S-NPH2 12 −116.7586 1.50001.51823 58.90 S-NSL3 13 103.3786 3.0000 14 92.3565 7.0000 1.51633 64.14S-BSL7 15 −37.9424 1.0000 1.49700 81.54 S-FPL51 16 43.2698 5.2000 17−49.2412 2.0000 1.89190 37.13 S-LAH92 18 −1735.8345 DD[18] 19 68.12534.8214 1.43875 94.94 S-FPL53 20 −112.7072 0.1202 21 74.8115 1.00001.90366 31.34 S-LAH95 22 44.7331 4.5000 1.43875 94.94 S-FPL53 23−298.7315 0.1200 24 64.6328 4.0000 1.69680 55.53 S-LAL14 25 786.55042.0000 26 −445.4631 1.0000 1.71300 53.87 S-LAL8 27 22.4752 6.50001.65844 50.88 S-BSM25 28 102.3007 DD[28]

TABLE 25B Example 7 Sn R D nd ν Material 29 (St) ∞ 2.1937 30 140.99851.5000 1.88300 40.76 S-LAH58 31 94.3166 3.0000 1.80000 29.84 S-NBH55 32284.3480 1.8000 33 22.1963 5.0100 1.43875 94.94 S-FPL53 34 −60.72350.8000 1.72916 54.68 S-LAL18 35 28.1470 22.8200 36 24.5569 3.02931.67270 32.10 S-TIM25 37 −47.5999 0.5000 38 −74.5114 2.5000 1.4874970.24 S-FSL5 39 −14.5296 1.0000 1.88300 40.76 S-LAH58 40 −22.6725 0.200041 17.1057 0.8000 1.72916 54.68 S-LAL18 42 7.7230 2.5000 43 −12.04521.0000 1.43875 94.94 S-FPL53 44 10.1743 2.0000 45 12.6862 2.0000 1.4387594.94 S-FPL53 46 −91.2525 25.0000 47 ∞ 1.2000 1.51633 64.14 S-BSL7 48 ∞15.7567

TABLE 26 Example 7 WIDE MIDDLE TELE Zr 1.0 7.1 50.0 f 58.9 416.5 2945.0FNo. 6.35 8.24 14.82 ω (°) 5.2 0.7 0.1 DD[10] 119.5806 273.1604 327.0120DD[18] 293.5368 115.0081 2.2805 DD[28] 2.9992 27.9481 86.8241

TABLE 27 Example 7 TL 668.6 f1 515.3 f2 −44.5 f3 68.7 f4 −31.5 f31 97.6

TABLE 28 Example 7 Bfd 41.55 Bf_1300 42.73 Bf_1426 43.00 Bf_1450 43.02Bf_1450 43.02 Bf_1460 43.03 Bf_1530 43.05 Bf_1550 43.04 Bf_1570 43.02Bf_1651 42.88 Bf_1653 42.87 Bf_1696 42.74 Bf_1725 42.62 Bf_1750 42.50Bf_1870 41.73 Bf_1940 41.10 Bf_1970 40.79 Bf_2050 39.83 Bf_2120 38.83Bf_2325 35.07

EXAMPLE 8

A configuration of a variable magnification optical system of Example 8and a movement trajectory are illustrated in FIG. 16 . The variablemagnification optical system of Example 8 consists of, in order from theobject side to the image side, the first lens group G1 having a positiverefractive power, the second lens group G2 having a negative refractivepower, the third lens group G3 having a positive refractive power, theaperture stop St, and the fourth lens group G4 having a negativerefractive power. During zooming, the first lens group G1, the aperturestop St, and the fourth lens group G4 are fixed with respect to theimage plane Sim, and the second lens group G2 and the third lens groupG3 are moved along the optical axis Z by changing an interval betweeneach other. The first lens group G1 consists of lenses L11 to L19. Thesecond lens group G2 consists of the lenses L21 to L25. The third lensgroup G3 consists of the lenses L31 to L36. The fourth lens group G4consists of lenses L41 to L52. The variable magnification optical systemof Example 8 has an aspherical surface. For the variable magnificationoptical system of Example 8, basic lens data is shown in Table 29A andTable 29B, and specifications and a variable surface interval are shownin Table 30. Various data are shown in Table 31 and Table 32, andaspherical coefficients are shown in Table 33. Each aberration diagramis illustrated in FIG. 17 . All materials shown in Table 29A and Table29B are manufactured by OHARA INC.

In the table of the basic lens data, a mark * is added to a surfacenumber of the aspherical surface, and a numerical value of a paraxialradius of curvature is written in the field of a radius of curvature ofthe aspherical surface. In the table of the aspherical coefficient, thefield of Sn shows the surface number of the aspherical surface, andfields of KA and Am (m=3, 4, 5, . . . 20) show numerical values of theaspherical coefficient for each aspherical surface. In the numericalvalue of the aspherical coefficient in Table 33, “E±n” (n: integer)means “×10^(±n)”. KA and Am are aspherical coefficients in an asphericalexpression represented by the following expression.

Zd=C×h ²/{1+(1−KA×C ² ×h ²)^(1/2) }+ΣAm×h ^(m)

where

Zd: aspherical depth (length of perpendicular line drawn from point onaspherical surface at height h to plane that passes through apex ofaspherical surface and is perpendicular to optical axis)

h: height (distance from optical axis to lens surface)

C: reciprocal of paraxial radius of curvature

KA, Am: aspherical coefficient

In the aspherical expression, Σ means a total sum related to m. Theabove writing method related to the aspherical surface is the same inthe following examples having aspherical surfaces.

TABLE 29A Example 8 Sn R D nd ν Material 1 608.0344 4.0782 1.48749 70.24S-FSL5 2 206.2500 12.4482 1.43875 94.66 S-FPL55 3 −470.1050 7.1152 4484.6132 14.3062 1.43875 94.66 S-FPL55 5 −197.6232 3.6366 1.51633 64.14S-BSL7 6 820.8117 6.2716 7 108.8304 14.9387 1.43875 94.66 S-FPL55 8665.1004 3.5050 1.92286 18.90 S-NPH2 9 400.2462 1.1648 10 415.01206.0443 1.54814 45.78 S-TIL1 11 1014.1944 0.1200 12 133.2757 18.65521.49700 81.54 S-FPL51 13 −229.6380 4.4585 1.53775 74.70 S-FPM3 14138.8571 DD[14] *15  −249.5451 1.2091 1.95375 32.32 S-LAH98 16 61.91742.1546 17 −65.3189 1.8364 1.95375 32.32 S-LAH98 18 77.4214 2.48581.80518 25.42 S-TIH6 19 2823.3303 6.1492 20 −234.7929 5.5582 1.8589622.73 S-NPH5 21 −19.8177 1.2733 1.89190 37.13 S-LAH92 22 −129.8830DD[22] *23  112.5168 2.9296 1.49700 81.54 S-FPL51 24 −132.5374 12.168125 264.7784 1.4983 1.80518 25.42 S-TIH6 26 56.1658 6.8372 1.43875 94.66S-FPL55 27 −117.6463 3.8124 *28  −2726.8215 4.2521 1.49700 81.54 S-FPL51*29  −118.2343 4.1350 30 92.3756 4.2793 1.43875 94.66 S-FPL55 31−166.5478 2.0895 1.96300 24.11 S-TIH57 32 −125.2623 DD[32]

TABLE 29B Example 8 Sn R D nd ν Material 33 (St) ∞ 2.0819 34 −1340.13961.2002 1.48749 70.24 S-FSL5 35 46.1665 4.3082 1.51742 52.43 S-NSL36 36−28.4676 1.2000 1.65100 56.24 S-LAL54Q 37 375.2211 0.8333 38 −55.99444.5696 1.48749 70.24 S-FSL5 39 43.8130 4.8035 40 39.8177 3.2659 1.8340037.21 S-LAH60V 41 −409.0846 1.8565 1.73800 32.33 S-NBH53V 42 88.68842.9906 43 59.9658 3.8823 1.67300 38.26 S-NBH52V 44 −78.7700 0.1720 4591.1044 1.2404 1.48749 70.24 S-FSL5 46 14.3937 8.4910 1.64769 33.79S-TIM22 47 43.4392 3.9464 48 1177.6843 2.5069 1.89286 20.36 S-NPH4 4911.3614 5.3491 1.53775 74.70 S-FPM3 50 43.8795 19.4869 51 251.66722.1917 1.89286 20.36 S-NPH4 52 −149.7461 11.0215 53 ∞ 1.0000 1.5163364.14 S-BSL7 54 ∞ 16.0149

TABLE 30 Example 8 WIDE MIDDLE TELE Zr 1.0 3.1 9.7 f 50.7 157.9 492.0FNo. 6.00 5.97 6.07 ω (°) 9.4 3.0 1.0 DD[14] 34.7767 78.1325 101.1073DD[22] 105.3581 47.1239 0.4124 DD[321 2.7005 17.5790 41.3157

TABLE 31 Example 8 TL 404.3 f1 211.5 f2 −29.5 f3 54.8 f4 −102.3 f31122.9

TABLE 32 Example 8 Bfd 27.70 Bf_1300 27.17 Bf_1426 27.09 Bf_1450 27.08Bf_1450 27.08 Bf_1460 27.07 Bf_1530 27.01 Bf_1550 27.00 Bf_1570 26.98Bf_1651 26.90 Bf_1653 26.90 Bf_1696 26.86 Bf_1725 26.82 Bf_1750 26.79Bf_1870 26.63 Bf_1940 26.52 Bf_1970 26.47 Bf_2050 26.32 Bf_2120 26.18Bf_2325 25.65

TABLE 33 Example 8 Sn 15 23 28 29 KA 1.0000000E+00 1.0000000E+001.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 0.0000000E+000.0000000E+00 A4 5.0980967E−07 −3.6254106E−07 2.7620064E−084.0035834E−08 A5 3.9354495E−08 2.6623449E−08 3.3526579E−09 1.5772142E−09A6 1.0412285E−09 −2.2257738E−09 7.4784262E−11 −1.7344856E−11 A7−1.9997382E−10 −3.3960366E−11 8.4531316E−12 −5.0345885E−12 A8−9.4648998E−12 2.4268412E−11 −9.7518030E−14 −1.7312973E−13 A9−2.5972049E−13 −7.3961321E−13 −1.5074665E−15 −2.8389625E−14 A102.4539895E−14 −1.9870087E−13 −3.2432776E−15 −1.3449759E−15 A11−1.6904717E−15 1.4336488E−14 3.9350245E−18 −4.4415276E−17 A121.3807177E−16 −4.0413029E−16 −1.8218984E−18 4.7709027E−18 A138.3359638E−18 −5.2764647E−17 2.8708095E−19 −1.1006639E−18 A143.1707623E−18 3.3780403E−18 −2.9820760E−21 2.7403645E−20 A151.0306301E−19 2.9926023E−19 −1.9442888E−22 8.1467527E−22 A161.0230861E−21 −2.4625367E−21 4.9252408E−23 9.3189571E−23 A174.7576761E−22 −5.1499025E−22 2.9501141E−24 −1.2920571E−23 A18−6.2958213E−23 2.1118404E−24 3.9341402E−25 −2.9772750E−25 A19−5.1708229E−24 1.3211718E−24 −4.5746494E−26 4.0466074E−26 A20−2.2723346E−25 −2.4251436E−25 −4.5071150E−27 2.0372667E−27

EXAMPLE 9

A configuration of a variable magnification optical system of Example 9and a movement trajectory are illustrated in FIG. 18 . The variablemagnification optical system of Example 9 consists of, in order from theobject side to the image side, the first lens group G1 having a positiverefractive power, the second lens group G2 having a negative refractivepower, the third lens group G3 having a positive refractive power, theaperture stop St, and the fourth lens group G4 having a positiverefractive power. During zooming, the first lens group G1, the aperturestop St, and the fourth lens group G4 are fixed with respect to theimage plane Sim, and the second lens group G2 and the third lens groupG3 are moved along the optical axis Z by changing an interval betweeneach other. The first lens group G1 consists of the lenses L11 to L19.The second lens group G2 consists of the lenses L21 to L25. The thirdlens group G3 consists of lenses L31 to 38. The fourth lens group G4consists of the lenses L41 to L52. For the variable magnificationoptical system of Example 9, basic lens data is shown in Table 34A andTable 34B, and specifications and a variable surface interval are shownin Table 35. Various data are shown in Table 36 and Table 37, andaspherical coefficients are shown in Table 38. Each aberration diagramis illustrated in FIG. 19 . All materials shown in Table 34A and Table34B are manufactured by OHARA INC.

TABLE 34A Example 9 Sn R D nd ν Material 1 −1299.9288 5.4651 1.5182358.90 S-NSL3 2 520.2595 12.1240 1.61800 63.33 S-PHM52 3 −742.7481 0.12024 519.4882 23.0365 1.43875 94.66 S-FPL55 5 −326.6357 3.5001 1.4874970.24 S-FSL5 6 672.4794 37.2054 7 254.9073 13.0281 1.43875 94.66 S-FPL558 5040.7140 3.5006 1.80518 25.42 S-TIH6 9 892.7001 1.7076 10 635.65946.1193 1.51633 64.14 S-BSL7 11 2165.8524 0.2400 12 265.3663 23.34581.49700 81.54 S-FPL51 13 −810.9531 7.1048 1.53775 74.70 S-FPM3 14307.0444 DD[14] *15  −429.2186 1.2002 1.85400 40.38 L-LAH85V 16 129.97702.3109 17 −121.6688 1.4913 1.95375 32.32 S-LAH98 18 100.1965 2.75671.85478 24.80 S-NBH56 19 1831.4008 9.7567 20 −431.7438 9.1027 1.8589622.73 S-NPH5 21 −37.3032 3.1873 1.89190 37.13 S-LAH92 22 −309.0675DD[22] *23  212.4151 2.7112 1.49700 81.54 S-FPL51 24 −236.3700 0.9211 25−145.7015 1.8817 1.69895 30.13 S-TIM35 26 22396.8310 2.8139 1.8589622.73 S-NPH5 27 −190.6770 0.8900 28 466.2306 2.3477 1.85478 24.80S-NBH56 29 105.3843 4.0406 1.43875 94.66 S-FPL55 30 −214.2560 0.6602 31190.2479 7.1483 1.43875 94.66 S-FPL55 32 −300.0746 2.8862 1.85150 40.78S-LAH89 33 −261.4437 2.0634 *34  4401.4516 2.5777 1.49700 81.54 S-FPL51*35  −217.1293 DD[35]

TABLE 34B Example 9 Sn R D nd ν Material 36 (St) ∞ 4.1638 37 742.15332.4835 1.48749 70.24 S-FSL5 38 133.8453 9.6930 1.51742 52.43 S-NSL36 39−52.3794 1.8597 1.65100 56.24 S-LAL54Q 40 −1717.1431 20.3558 41−108.1406 9.0979 1.48749 70.24 S-FSL5 42 67.7056 3.6877 43 74.48112.6689 1.90525 35.04 S-LAH93 44 −351.6126 3.8807 45 −696.9155 1.63541.69895 30.13 S-TIM35 46 160.8667 12.2086 47 99.6203 1.5997 1.9052535.04 S-LAH93 48 −147.7203 0.9948 49 411.1244 3.4828 1.48749 70.24S-FSL5 50 37.0932 10.3867 1.51633 64.14 S-BSL7 51 78.6743 2.7742 52657.0130 8.1219 1.89286 20.36 S-NPH4 53 21.2140 6.8479 1.53775 74.70S-FPM3 54 28.0470 23.2316 55 76.9234 4.3834 1.95375 32.32 S-LAH98 56−114.5347 22.0000 57 ∞ 1.0000 1.51633 64.14 S-BSL7 58 ∞ 1.1107

TABLE 35 Example 9 WIDE MIDDLE TELE Zr 1.0 3.2 10.0 f 96.8 306.0 967.6FNo. 6.00 6.00 7.38 ω (°) 4.9 1.6 0.5 DD[14] 171.2020 242.3067 279.7517DD[22] 193.5093 92.3017 5.7895 DD[35] 19.3042 49.4071 98.4743

TABLE 36 Example 9 TL 738.9 f1 449.3 f2 −56.3 f3 97.6 f4 126.0 f31 225.6

TABLE 37 Example 9 Bfd 23.77 Bf_1300 23.70 Bf_1426 23.71 Bf_1450 23.71Bf_1450 23.71 Bf_1460 23.71 Bf_1530 23.71 Bf_1550 23.70 Bf_1570 23.70Bf_1651 23.68 Bf_1653 23.67 Bf_1696 23.66 Bf_1725 23.64 Bf_1750 23.63Bf_1870 23.53 Bf_1940 23.46 Bf_1970 23.42 Bf_2050 23.31 Bf_2120 23.19Bf_2325 22.72

TABLE 38 Example 9 Sn 15 23 34 35 KA 1.0000000E+00 1.0000000E+001.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 0.0000000E+000.0000000E+00 A4 7.0516760E−08 −7.0754361E−08 1.8783771E−08−1.2117220E−08 A5 5.4541983E−09 1.7030419E−09 4.1564839E−103.5636600E−10 A6 4.3287789E−11 −7.9077820E−11 −5.7557058E−118.6492791E−12 A7 4.9902716E−12 9.1682810E−13 −2.6203141E−121.8653297E−12 A8 6.2976350E−13 1.8011224E−13 −4.1892332E−141.1833179E−13 A9 −7.3826284E−15 −2.9025238E−15 −7.0832786E−16−1.2444811E−15 A10 8.1564405E−16 −4.0209634E−16 2.6296518E−172.5381464E−16 A11 −3.9276133E−17 1.7920865E−17 2.4660632E−185.0038403E−19 A12 4.9147017E−18 −9.5332577E−20 3.3901988E−192.6784816E−19 A13 1.0315866E−19 −1.9318605E−20 −5.8760109E−211.7605145E−20 A14 1.7563470E−20 3.3805520E−21 2.2437206E−229.7806439E−22 A15 −2.5443780E−21 4.2572553E−23 −7.1075932E−233.5475728E−26 A16 −2.5998307E−22 2.6296369E−24 2.5735439E−242.4913822E−24 A17 −6.4558227E−24 2.5772532E−25 3.7672757E−252.3633082E−25 A18 2.8484283E−25 −4.3858631E−26 1.3316362E−261.0328971E−26 A19 1.4588159E−26 5.6920768E−28 2.9858390E−28−1.8255105E−28 A20 7.9514005E−28 3.9372417E−29 7.4352778E−30−2.2370745E−29

EXAMPLE 10

A configuration of a variable magnification optical system of Example 10and a movement trajectory are illustrated in FIG. 20 . The variablemagnification optical system of Example 10 consists of, in order fromthe object side to the image side, the first lens group G1 having apositive refractive power, the second lens group G2 having a negativerefractive power, the third lens group G3 having a positive refractivepower, the aperture stop St, and the fourth lens group G4 having apositive refractive power. During zooming, the first lens group G1, theaperture stop St, and the fourth lens group G4 are fixed with respect tothe image plane Sim, and the second lens group G2 and the third lensgroup G3 are moved along the optical axis Z by changing an intervalbetween each other. The first lens group G1 consists of the lenses L11to L15. The second lens group G2 consists of the lenses L21 to 24. Thethird lens group G3 consists of the lenses L31 to 34. The fourth lensgroup G4 consists of the lenses L41 to 57. For the variablemagnification optical system of Example 10, basic lens data is shown inTable 39A and Table 39B, and specifications and a variable surfaceinterval are shown in Table 40. Various data are shown in Table 41 andTable 42, and each aberration diagram is illustrated in FIG. 21 . Allmaterials shown in Table 39A and Table 39B are manufactured by OHARAINC.

TABLE 39A Example 10 Sn R D nd ν Material 1 191.6339 4.0000 1.5163364.14 S-BSL7 2 125.0115 21.0000  1.49700 81.54 S-FPL51 3 −462.86191.0000 4 151.1321 15.0000  1.49700 81.54 S-FPL51 5 −448.9555 4.00001.79952 42.22 S-LAH52 6 182.6560 5.0000 7 114.9032 12.0000  1.4970081.54 S-FPL51 8 260.6024 DD[8]  9 53.6145 5.0000 1.96300 24.11 S-TIH5710 −60.8515 2.0100 1.80610 40.93 S-LAH53 11 21.6485 6.0000 12 −19.31512.0000 1.71300 53.87 S-LAL8 13 −128.5992 5.5000 14 −18.6876 6.00001.67270 32.10 S-TIM25 15 −19.1916 DD[15] 16 254.6938 4.0000 1.4970081.54 S-FPL51 17 −91.9227 0.2000 18 38.3915 4.0000 1.49700 81.54 S-FPL5119 −684.7849 0.5000 20 175.5845 1.6350 1.80400 46.58 S-LAH65V 21 25.27635.0100 1.53775 74.70 S-FPM3 22 −604.0159 DD[22]

TABLE 39B Example 10 Sn R D nd ν Material 23 (St) ∞ 1.8731 24 84.51305.0000 1.74400 44.79 S-LAM2 25 −61.3409 1.0000 26 −28.6458 1.00001.83400 37.21 S-LAH60V 27 105.0826 4.0100 1.51742 52.43 S-NSL36 28−23.3224 0.2000 29 −118.9121 1.0000 1.69680 55.53 S-LAL14 30 73.89023.6522 31 −160.2887 1.0000 1.69680 55.53 S-LAL14 32 74.5836 0.2000 3319.6292 4.6950 1.80518 25.42 S-TIH6 34 39.6811 1.0000 35 87.2130 1.77641.60311 60.64 S-BSM14 36 21.1995 1.5000 37 73.7321 3.0465 1.64850 53.02S-BSM71 38 −59.7021 0.1000 39 22.7123 4.0000 1.54814 45.78 S-TIL1 40−28.5331 1.0000 1.84666 23.78 S-TIH53 41 120.0457 2.0000 42 −42.69051.0000 1.80400 46.53 S-LAH65VS 43 27.5997 3.7239 1.80440 39.59 S-LAH6344 39.4151 2.0000 45 −52.7430 2.5430 1.75500 52.32 S-YGH51 46 28.15675.0100 1.59551 39.24 S-TIM8 47 −23.3379 25.5624 48 65.9854 3.00001.84666 23.78 S-TIH53 49 174.2359 0.7000 50 91.9800 4.5000 1.51633 64.14S-BSL7 51 −28.1669 1.0000 1.84666 23.78 S-TIH53 52 −62.7438 6.0000 53 ∞1.0000 1.51633 64.14 S-BSL7 54 ∞ 7.9214

TABLE 40 Example 10 WIDE MIDDLE TELE Zr 1.0 6.2 38.0 f 20.6 126.8 782.0FNo. 4.20 4.87 7.20 ω (°) 15.6 2.5 0.4 DD[8] 18.5649 103.2171 133.1145DD[15] 187.7800 79.3964 0.9006 DD[22] 3.2639 26.9953 75.5937

TABLE 41 Example 10 TL 415.1 f1 224.1 f2 −28.3 f3 61.2 f4 112.0 f31136.4

TABLE 42 Example 10 Bfd 14.58 Bf_1300 14.75 Bf_1426 14.83 Bf_1450 14.85Bf_1450 14.85 Bf_1460 14.85 Bf_1530 14.88 Bf_1550 14.88 Bf_1570 14.88Bf_1651 14.89 Bf_1653 14.89 Bf_1696 14.88 Bf_1725 14.87 Bf_1750 14.86Bf_1870 14.76 Bf_1940 14.67 Bf_1970 14.63 Bf_2050 14.48 Bf_2120 14.31Bf_2325 13.59

EXAMPLE 11

A configuration of a variable magnification optical system of Example 11and a movement trajectory are illustrated in FIG. 22 . The variablemagnification optical system of Example 11 consists of, in order fromthe object side to the image side, the first lens group G1 having apositive refractive power, the second lens group G2 having a negativerefractive power, the third lens group G3 having a positive refractivepower, the aperture stop St, and the fourth lens group G4 having anegative refractive power. During zooming, the first lens group G1, theaperture stop St, and the fourth lens group G4 are fixed with respect tothe image plane Sim, and the second lens group G2 and the third lensgroup G3 are moved along the optical axis Z by changing an intervalbetween each other. The first lens group G1 consists of the lenses L11to L19. The second lens group G2 consists of the lenses L21 to L25. Thethird lens group G3 consists of the lenses L31 to 38. The fourth lensgroup G4 consists of the lenses L41 to L52. For the variablemagnification optical system of Example 11, basic lens data is shown inTable 43A and Table 43B, and specifications and a variable surfaceinterval are shown in Table 44. Various data are shown in Table 45 andTable 46, and aspherical coefficients are shown in Table 47. Eachaberration diagram is illustrated in FIG. 23 . All materials shown inTable 43A and Table 43B except CAF2 are manufactured by OHARA INC.

TABLE 43A Example 11 Sn R D nd ν Material  1 780.6949 3.5006 1.4874970.24 S-FSL5  2 167.9672 1.8019  3 210.0960 11.6780 1.43387 95.18 CAF2 4 −571.0053 0.1201  5 728.3125 9.0432 1.43875 94.66 S-FPL55  6−290.1276 3.5003 1.62041 60.29 S-BSM16  7 −762.8468 6.0681  8 104.590614.2928 1.43875 94.66 S-FPL55  9 706.4555 5.0001 1.89286 20.36 S-NPH4 10369.1015 15.0045 11 319.2933 7.2701 1.53172 48.84 S-TIL6 12 837.93420.1200 13 143.7060 15.9983 1.43875 94.66 S-FPL55 14 −920.1831 4.73461.49700 81.54 S-FPL51 15 123.9324 DD[15] *16  −268.0411 1.3796 1.8610037.10 L-LAH94 17 56.3165 2.1199 18 −66.1664 1.6227 1.95375 32.32 S-LAH9819 113.6831 3.1564 1.80518 25.42 S-TIH6 20 −1429.4895 4.9726 21−196.9681 5.3329 1.85896 22.73 S-NPH5 22 −19.1552 1.9060 1.89190 37.13S-LAH92 23 −123.7732 DD[23] *24  99.3590 3.3394 1.49700 81.54 S-FPL51 25−147.8514 1.6356 26 −303.8434 1.2140 1.90525 35.04 S-LAH93 27 −110.14441.2286 1.48749 70.24 S-FSL5 28 −1862.4500 0.1245 29 361.8522 1.20221.80000 29.84 S-NBH55 30 52.6867 4.8065 1.43875 94.66 S-FPL55 31−132.5238 7.5335 *32  401.8606 4.7669 1.49700 81.54 S-FPL51 *33 −123.3489 12.8515 34 89.8462 3.2365 1.43875 94.66 S-FPL55 35 −115.93911.7777 1.85150 40.78 S-LAH89 36 −131.5321 DD[36]

TABLE 43B Example 11 Sn R D nd ν Material 37 (St) ∞ 2.0819 38 576.51561.3168 1.58913 61.13 S-BAL35 39 73.6208 5.7750 1.49700 81.54 S-FPL51 40−14.8048 1.2146 1.51742 52.43 S-NSL36 41 158.6220 2.0686 42 −35.83551.4496 1.49700 81.54 S-FPL51 43 38.5875 1.1226 44 35.1050 2.9739 1.9052535.04 S-LAH93 45 −206.0747 10.3076 46 −165.8903 1.2229 1.62588 35.70S-TIM1 47 88.6506 0.6595 48 56.8519 2.5149 1.85150 40.78 S-LAH89 49−82.7460 0.4935 50 118.6771 1.2062 1.49700 81.54 S-FPL51 51 26.99933.8086 1.54814 45.78 S-TIL1 52 44.2398 4.9455 53 178.5228 1.6865 1.9630024.11 S-TIH57 54 13.3859 2.1759 1.53775 74.70 S-FPM3 55 23.0068 2.943156 99.4121 2.1917 1.90366 31.34 S-LAH95 57 −77.8706 3.0000 58 ∞ 1.00001.51633 64.14 S-BSL7 59 ∞ 27.6162

TABLE 44 Example 11 WIDE MIDDLE TELE Zr 1.0 3.2 10.0 f 50.4 159.4 504.2FNo. 6.06 6.05 6.09 ω (°) 9.4 2.9 0.9 DD[15] 40.1224 85.7736 109.8310DD[23] 111.2468 49.8882 0.4674 DD[36] 2.6194 18.3268 43.6902

TABLE 45 Example 11 TL 399.8 f1 229.9 f2 −31.3 f3 56.4 f4 −67.7 f31120.1

TABLE 46 Example 11 Bfd 31.28 Bf_1300 30.98 Bf_1426 30.93 Bf_1450 30.92Bf_1450 30.92 Bf_1460 30.91 Bf_1530 30.87 Bf_1550 30.86 Bf_1570 30.85Bf_1651 30.79 Bf_1653 30.78 Bf_1696 30.75 Bf_1725 30.72 Bf_1750 30.70Bf_1870 30.56 Bf_1940 30.46 Bf_1970 30.42 Bf_2050 30.29 Bf_2120 30.15Bf_2325 29.66

TABLE 47 Example 11 Sn 16 24 32 33 KA 1.0000000E+00 1.0000000E+001.0000000E+00 1.0000000E+00 A3 0.0000000E+00 0.0000000E+00 0.0000000E+000.0000000E+00 A4 5.7994375E−07 −3.6845628E−07 1.1826809E−07−9.2366048E−08 A5 4.5904615E−08 1.4952370E−08 −4.8693622E−104.3255797E−10 A6 1.4942507E−09 −2.6330068E−09 −9.4793161E−11−1.1228624E−10 A7 −1.7205480E−10 −2.0298003E−11 −2.3695337E−11−3.8296919E−12 A8 −1.1956181E−11 2.4900263E−11 −3.5004056E−13−4.2267579E−13 A9 −2.1686788E−15 −5.2164561E−13 8.3598728E−15−3.3399811E−14 A10 −1.0396394E−14 −1.8925408E−13 −1.8355821E−15−2.3463878E−15 A11 −4.1574507E−15 1.4967448E−14 −2.8096441E−19−3.4679353E−16 A12 4.9817817E−17 −3.5722677E−16 9.3253704E−18−3.8687863E−17 A13 −8.5599684E−19 −5.5751607E−17 −1.6625421E−18−9.5112175E−19 A14 1.9934546E−18 3.4061664E−18 8.7558461E−20−1.3121730E−19 A15 1.4970972E−19 2.8624358E−19 1.3403886E−21−9.8168169E−21 A16 1.3048840E−22 −4.4928114E−21 4.0090607E−225.6606804E−22 A17 6.5186940E−22 −6.6686421E−22 2.5784633E−231.3278361E−24 A18 −4.8717666E−23 −7.8121018E−24 3.0624425E−254.6261726E−26 A19 3.4890952E−24 1.8841217E−24 −4.0851136E−25−1.1410085E−25 A20 4.4394243E−26 −2.7127052E−25 −1.3345348E−267.9865098E−27

Table 48 and Table 49 show corresponding values of ConditionalExpression (1) of the variable magnification optical systems of Examples1 to 11. Here, a symbol of “Bf_numerical value” used in Table 4 and thelike is used as “BfIR” of Conditional Expression (1).

TABLE 48 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6(Bfd − Bf_1300)/ft −0.00036 −0.00023 −0.00013 −0.00020 −0.00023 −0.00024(Bfd − Bf_1426)/ft −0.00050 −0.00031 −0.00022 −0.00025 −0.00029 −0.00030(Bfd − Bf_1450)/ft −0.00053 −0.00032 −0.00024 −0.00026 −0.00030 −0.00031(Bfd − Bf_1450)/ft −0.00053 −0.00032 −0.00024 −0.00026 −0.00030 −0.00031(Bfd − Bf_1460)/ft −0.00054 −0.00033 −0.00024 −0.00026 −0.00030 −0.00031(Bfd − Bf_1530)/ft −0.00059 −0.00035 −0.00027 −0.00027 −0.00031 −0.00032(Bfd − Bf_1550)/ft −0.00060 −0.00035 −0.00028 −0.00027 −0.00031 −0.00032(Bfd − Bf_1570)/ft −0.00061 −0.00036 −0.00028 −0.00027 −0.00031 −0.00032(Bfd − Bf_1651)/ft −0.00063 −0.00035 −0.00029 −0.00024 −0.00029 −0.00030(Bfd − Bf_1653)/ft −0.00063 −0.00035 −0.00029 −0.00024 −0.00029 −0.00030(Bfd − Bf_1696)/ft −0.00063 −0.00034 −0.00028 −0.00022 −0.00027 −0.00027(Bfd − Bf_1725)/ft −0.00062 −0.00033 −0.00027 −0.00020 −0.00025 −0.00025(Bfd − Bf_1750)/ft −0.00061 −0.00032 −0.00026 −0.00018 −0.00023 −0.00023(Bfd − Bf_1870)/ft −0.00051 −0.00021 −0.00027 −0.00005 −0.00010 −0.00010(Bfd − Bf_1940)/ft −0.00041 −0.00011 −0.00009 0.00007 0.00001 0.00002(Bfd − Bf_1970)/ft −0.00035 −0.00006 −0.00004 0.00013 0.00007 0.00008(Bfd − Bf_2050)/ft −0.00016 0.00010 0.00010 0.00031 0.00025 0.00026 (Bfd− Bf_2120)/ft 0.00006 0.00027 0.00026 0.00050 0.00044 0.00045 (Bfd −Bf_2325)/ft 0.00101 0.00100 0.00093 0.00128 0.00118 0.00121

TABLE 49 Example 7 Example 8 Example 9 Example 10 Example 11 (Bfd −Bf_1300)/ft −0.00040 0.00106 0.00007 −0.00022 0.00058 (Bfd − Bf_1426)/ft−0.00049 0.00122 0.00006 −0.00032 0.00069 (Bfd − Bf_1450)/ft −0.000500.00126 0.00006 −0.00034 0.00071 (Bfd − Bf_1450)/ft −0.00050 0.001260.00006 −0.00034 0.00071 (Bfd − Bf_1460)/ft −0.00050 0.00127 0.00006−0.00035 0.00072 (Bfd − Bf_1530)/ft −0.00051 0.00138 0.00007 −0.000380.00080 (Bfd − Bf_1550)/ft −0.00051 0.00142 0.00007 −0.00038 0.00083(Bfd − Bf_1570)/ft −0.00050 0.00145 0.00007 −0.00039 0.00085 (Bfd −Bf_1651)/ft −0.00045 0.00161 0.00010 −0.00039 0.00097 (Bfd − Bf_1653)/ft−0.00045 0.00161 0.00010 −0.00039 0.00097 (Bfd − Bf_1696)/ft −0.000400.00171 0.00012 −0.00038 0.00105 (Bfd − Bf_1725)/ft −0.00036 0.001770.00013 −0.00037 0.00110 (Bfd − Bf_1750)/ft −0.00032 0.00183 0.00015−0.00035 0.00115 (Bfd − Bf_1870)/ft −0.00006 0.00216 0.00024 −0.000230.00142 (Bfd − Bf_1940)/ft 0.00015 0.00239 0.00032 −0.00012 0.00161 (Bfd− Bf_1970)/ft 0.00026 0.00249 0.00036 −0.00006 0.00170 (Bfd −Bf_2050)/ft 0.00058 0.00279 0.00047 0.00013 0.00196 (Bfd − Bf_2120)/ft0.00092 0.00309 0.00060 0.00035 0.00223 (Bfd − Bf_2325)/ft 0.002200.00416 0.00109 0.00127 0.00320

Table 50 and Table 51 show corresponding values of ConditionalExpressions (2) to (31) of the variable magnification optical systems ofExamples 1 to 11.

TABLE 50 Expression Number Example 1 Example 2 Example 3 Example 4Example 5 Example 6  (2) θ1ave 2.0 2.0 2.1 2.0 2.1 2.1  (3) θ1Pave −θ1Nave 0.0 0.1 0.1 0.2 0.0 0.0  (4) θ3ave 2.0 1.9 1.9 1.9 1.9 1.9  (5)ft/TL 1.9 2.1 3.0 3.0 3.6 3.6  (6) θ1ave/θ2ave 1.2 1.0 1.1 1.0 1.1 1.1 (7) θ3ave/θ2ave 1.2 1.0 1.0 1.0 1.0 1.0  (8) ν1ave 70.2 75.6 75.3 75.881.5 81.5  (9) θ4ave 1.7 1.9 1.9 1.9 1.8 1.9 (10) θ2ave 1.7 2.0 1.9 1.91.9 1.9 (11) θ1Pave 2.0 2.1 2.1 2.1 2.1 2.1 (12) θ1Nave 2.0 2.0 2.1 1.92.1 2.1 (13) θ2Pave − θ2Nave −0.6 −0.3 −0.5 −0.2 −0.2 −0.2 (14) θ3Pave −θ3Nave 0.2 0.3 0.3 0.3 0.3 0.3 (15) θ4Pave − θ4Nave −0.1 0.1 0.0 −0.5−0.4 0.0 (16) ν1Pave − ν1Nave 28.4 34.3 29.4 33.7 27.6 27.6 (17) ν2Pave− ν2Nave −23.7 −18.8 −23.9 −15.5 −15.5 −15.5 (18) ν3Pave − ν3Nave 32.738.8 28.5 30.1 30.1 30.1 (19) ν2ave 42.3 55.0 54.2 53.1 53.1 53.1 (20)ν3ave 71.1 62.4 62.4 63.1 63.1 63.1 (21) ν4ave 44.9 57.1 56.9 56.0 53.056.0 (22) θ2Pave 1.4 1.8 1.6 1.8 1.8 1.8 (23) θ2Nave 1.9 2.0 2.1 2.0 2.02.0 (24) θ4Pave 1.7 1.9 1.9 1.4 1.5 1.9 (25) ft/f1 4.5 3.9 4.7 5.0 4.94.9 (26) ft/f1Pmax 4.6 2.9 6.7 5.0 6.1 6.6 (27) f2/fw −1.3 −1.9 −1.4−1.3 −0.6 −0.6 (28) f2Nmax/fw −1.0 −2.6 −2.6 −1.3 −0.5 −0.5 (29) f1/f2−6.7 −7.6 −8.9 −8.8 −9.6 −9.8 (30) f3/f2 −2.5 −2.2 −2.0 −1.8 −1.4 −1.4(31) TL/f31 2.8 4.3 5.1 4.8 6.9 5.6

TABLE 51 Expression Number Example 7 Example 8 Example 9 Example 10Example 11  (2) θ1ave 2.1 2.0 2.1 2.0 2.0  (3) θ1Pave − θ1Nave −0.1 0.00.2 0.0 0.0  (4) θ3ave 1.9 1.8 1.7 2.0 1.9  (5) ft/TL 4.4 1.2 1.3 1.91.3  (6) θ1ave/θ2ave 1.2 1.5 1.5 1.3 1.4  (7) θ3ave/θ2ave 1.1 1.3 1.21.2 1.4  (8) ν1ave 76.7 71.0 69.7 70.2 73.4  (9) θ4ave 1.9 1.9 1.9 1.71.8 (10) θ2ave 1.8 1.4 1.4 1.6 1.4 (11) θ1Pave 2.1 2.0 2.1 2.0 2.0 (12)θ1Nave 2.2 2.0 2.0 2.0 2.0 (13) θ2Pave − θ2Nave −0.1 −0.1 −0.2 −0.5 −0.2(14) θ3Pave − θ3Nave 0.3 0.6 0.5 0.2 0.1 (15) θ4Pave − θ4Nave 0.0 −0.4−0.3 −0.1 −0.1 (16) ν1Pave − ν1Nave 36.4 25.3 22.4 28.4 27.5 (17) ν2Pave− ν2Nave −17.7 −9.8 −12.8 −19.3 −11.4 (18) ν3Pave − ν3Nave 31.5 49.941.9 32.7 30.5 (19) ν2ave 52.1 30.0 31.5 37.8 30.9 (20) ν3ave 63.6 67.058.9 71.1 66.0 (21) ν4ave 61.1 49.3 51.9 44.9 54.6 (22) θ2Pave 1.8 1.31.3 1.4 1.3 (23) θ2Nave 1.9 1.4 1.5 1.9 1.5 (24) θ4Pave 1.9 1.7 1.8 1.71.7 (25) ft/f1 5.7 2.3 2.2 3.5 2.2 (26) ft/f1Pmax 8.5 2.8 2.4 3.9 1.8(27) f2/fw −0.8 −0.6 −0.6 −1.4 −0.6 (28) f2Nmax/fw −0.7 −0.5 −0.5 −1.0−0.5 (29) f1/f2 −11.6 −7.2 −8.0 −7.9 −7.3 (30) f3/f2 −1.5 −1.9 −1.7 −2.2−1.8 (31) TL/f31 6.9 3.3 3.3 3.0 3.3

As is perceived from the above data, in the variable magnificationoptical systems of Examples 1 to 11, an increase in size of the lenssystem is suppressed, and various types of aberration are favorablycorrected across a wide wavelength range of the visible range to theSWIR range. High optical characteristics are implemented.

Next, an imaging apparatus according to the embodiment of the presentdisclosure will be described. As one example of the imaging apparatus ofthe embodiment of the present disclosure, FIG. 24 illustrates aschematic configuration diagram of an imaging apparatus 100 using thevariable magnification optical system 1 according to the embodiment ofthe present disclosure. For example, examples of the imaging apparatus100 include a monitoring camera, a broadcasting camera, a movie imagingcamera, a video camera, and a digital camera.

The imaging apparatus 100 comprises the variable magnification opticalsystem 1, a filter 2 that is arranged on the image side of the variablemagnification optical system 1, and an imaging element 3 that isarranged on the image side of the filter 2. In FIG. 24 , a plurality oflenses comprised in the variable magnification optical system 1 areschematically illustrated.

The imaging element 3 converts an optical image formed by the variablemagnification optical system 1 into an electric signal. For example, acharge coupled device (CCD) or a complementary metal oxide semiconductor(CMOS) can be used as the imaging element 3. The imaging element 3 isarranged such that an imaging surface of the imaging element 3 matchesthe image plane of the variable magnification optical system 1.

The imaging apparatus 100 also comprises a signal processing unit 5 thatperforms calculation processing on an output signal from the imagingelement 3, a display unit 6 that displays an image formed by the signalprocessing unit 5, a zooming control unit 7 that controls zooming of thevariable magnification optical system 1, and a focusing control unit 8that controls focusing of the variable magnification optical system 1.

While only one imaging element 3 is illustrated in FIG. 24 , the imagingapparatus 100 may be configured to comprise a plurality of imagingelements. The imaging apparatus 100 may be configured to perform imagingusing separate imaging elements by causing light to branch for eachwavelength by inserting a spectral prism and/or a dichroic mirror at anylocation on the optical axis of the optical system. The imagingapparatus 100 may be an imaging apparatus in which an InGaAs detectorhaving sensitivity to the visible range to the SWIR range and a CMOS orthe like are combined, or may be an imaging apparatus in which anelement converting light in the SWIR range into light in the visiblerange and a CMOS or the like are combined.

While the technology of the present disclosure is described above usingthe embodiment and the examples, the technology of the presentdisclosure is not limited to the embodiment and the examples and can besubjected to various modifications. For example, the radius ofcurvature, the surface interval, the refractive index, the Abbe number,the partial dispersion ratio, and the aspherical coefficients of eachlens are not limited to values illustrated in each of the examples andmay have other values.

The magnification is also not limited to values of the examples. Thetechnology of the present disclosure can also be applied to a variablemagnification optical system that has a higher magnification or a lowermagnification than the examples. While the aberration diagrams of theexamples illustrate a range of g line (wavelength of 435.83 nm) to awavelength of 2325 nm, the technology of the present disclosure is notlimited to this wavelength range and can also be applied to a variablemagnification optical system of which a wavelength range is enlarged orreduced.

The imaging apparatus according to the embodiment of the presentdisclosure is not limited to a camera supporting the visible range andthe SWIR range. The technology of the present disclosure can also beapplied to a visible range camera, an SWIR range camera, a multispectralcamera, a hyperspectral camera, and a thermographic camera.

What is claimed is:
 1. A variable magnification optical systemcomprising, as lens groups consecutively in order from an object side toan image side: a first lens group; a second lens group; a third lensgroup; and a fourth lens group, wherein all intervals between adjacentlens groups are changed during changing magnification, and in a casewhere a d-line back focus in an air-conversion distance of the variablemagnification optical system at a telephoto end is denoted by Bfd, aback focus in any one wavelength from a wavelength of 1300 nm to awavelength of 2325.42 nm in the air-conversion distance of the variablemagnification optical system at the telephoto end is denoted by BfIR, ad-line focal length of the variable magnification optical system at thetelephoto end is denoted by ft, a focal length of the first lens groupis denoted by f1, a focal length of the second lens group is denoted byf2, a focal length of the third lens group is denoted by f3, arefractive index in F line is denoted by nF, a refractive index in Cline is denoted by nC, a refractive index in a wavelength of 1970.09 nmis denoted by n1970, and a partial dispersion ratio θ is defined asθ=(nC−n1970)/(nF−nC) for each lens of all lens groups, and an average ofθ of all lenses of the third lens group is denoted by θ3ave, ConditionalExpressions (1), (25-4), (30) and (4) are satisfied, which arerepresented by−0.0022<(Bfd−BfIR)/ft  (1)0.3<ft/f1<6  (25-4)−10<f3/f2<−0.1  (30)1.4<θ3 ave  (4).
 2. The variable magnification optical system accordingto claim 1, wherein in a case where a sum of Bfd and a distance on anoptical axis from a lens surface of the variable magnification opticalsystem closest to the object side to a lens surface of the variablemagnification optical system closest to the image side at the telephotoend is denoted by TL, Conditional Expression (5) is satisfied, which isrepresented by0.3<ft/TL  (5).
 3. The variable magnification optical system accordingto claim 1, wherein the variable magnification optical system comprisesonly four lens groups consisting of the first lens group, the secondlens group, the third lens group, and the fourth lens group in orderfrom the object side to the image side, as the lens groups, and thefirst lens group has a positive refractive power, the second lens grouphas a negative refractive power, the third lens group has a positiverefractive power, and the fourth lens group has a positive or negativerefractive power.
 4. The variable magnification optical system accordingto claim 1, wherein in a case where an average of θ of all lenses of thefirst lens group is denoted by θ1ave, and an average of θ of all lensesof the second lens group is denoted by θ2ave, Conditional Expression (6)is satisfied, which is represented by0.3<θ1 ave/θ2 ave<2  (6).
 5. The variable magnification optical systemaccording to claim 1, wherein in a case where an average of θ of alllenses of the third lens group is denoted by θ3ave, and an average of θof all lenses of the second lens group is denoted by θ2ave, ConditionalExpression (7) is satisfied, which is represented by0.3<θ3 ave/θ2 ave<2  (7).
 6. The variable magnification optical systemaccording to claim 1, wherein in a case where a d-line refractive indexfor each lens of all lens groups is denoted by nd, an Abbe number v isdefined as v=(nd−1)/(nF−nC), and an average of v of all lenses of thefirst lens group is denoted by v1ave, Conditional Expression (8) issatisfied, which is represented by50<v1 ave  (8).
 7. The variable magnification optical system accordingto claim 1, wherein in a case where an average of θ of all lenses of thefourth lens group is denoted by θ4 ave, Conditional Expression (9) issatisfied, which is represented by1.3<θ4 ave  (9).
 8. The variable magnification optical system accordingto claim 1, wherein in a case where an average of θ of all lenses of thesecond lens group is denoted by θ2ave, Conditional Expression (10) issatisfied, which is represented by1.2<θ2 ave  (10).
 9. The variable magnification optical system accordingto claim 1, wherein in a case where an average of θ of all positivelenses of the first lens group is denoted by θ1P ave, ConditionalExpression (11) is satisfied, which is represented by1.6<θ1P ave<2.3  (11).
 10. The variable magnification optical systemaccording to claim 1, wherein in a case where an average of θ of allnegative lenses of the first lens group is denoted by θ1N ave,Conditional Expression (12) is satisfied, which is represented byθ1N ave<2.3  (12).
 11. The variable magnification optical systemaccording to claim 1, wherein in a case where an average of θ of allpositive lenses of the second lens group is denoted by θ2P ave, and anaverage of θ of all negative lenses of the second lens group is denotedby θ2Nave, Conditional Expression (13) is satisfied, which isrepresented by−2<θ2P ave−θ2N ave  (13).
 12. The variable magnification optical systemaccording to claim 1, wherein in a case where an average of θ of allpositive lenses of the third lens group is denoted by θ3P ave, and anaverage of θ of all negative lenses of the third lens group is denotedby θ3Nave, Conditional Expression (14) is satisfied, which isrepresented byθ3P ave−θ3N ave<2  (14).
 13. The variable magnification optical systemaccording to claim 1, wherein in a case where an average of θ of allpositive lenses of the fourth lens group is denoted by θ4P ave, and anaverage of θ of all negative lenses of the fourth lens group is denotedby θ4Nave, Conditional Expression (15) is satisfied, which isrepresented by−2<04P ave−θ4N ave<2  (15).
 14. The variable magnification opticalsystem according to claim 1, wherein in a case where a d-line refractiveindex is denoted by nd, and an Abbe number v is defined asv=(nd−1)/(nF−nC) for each lens of all lens groups, an average of v ofall positive lenses of the first lens group is denoted by v1P ave, andan average of v of all negative lenses of the first lens group isdenoted by v1Nave, Conditional Expression (16) is satisfied, which isrepresented by15<v1P ave−v1N ave  (16).
 15. An imaging apparatus comprising: thevariable magnification optical system according to claim 1.